diff --git a/CITATION.cff b/CITATION.cff
index 4441d4fea83..def24639c31 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -642,7 +642,7 @@ references:
   title: graph
   abstract: 'graph: graph: A package to handle graph data structures'
   notes: Enhances
-  repository: https://bioconductor.org/
+  repository: https://bioc-release.r-universe.dev
   authors:
   - family-names: Gentleman
     given-names: R
@@ -657,7 +657,6 @@ references:
   - family-names: Shannon
     given-names: Paul
   year: '2026'
-  doi: 10.18129/B9.bioc.graph
 - type: software
   title: cpp11
   abstract: 'cpp11: A C++11 Interface for R''s C Interface'
diff --git a/src/rinterface_extra.c b/src/rinterface_extra.c
index 31db78a46e4..374a990cb64 100644
--- a/src/rinterface_extra.c
+++ b/src/rinterface_extra.c
@@ -69,6 +69,22 @@ enum igraph_versions {
 
 #define R_IGRAPH_VERSION_VAR ".__igraph_version__."
 
+#if R_VERSION >= R_Version(4, 5, 0)
+#  define IGRAPH_R_GET_VAR(sym, env, inherits) \
+    R_getVar((sym), (env), (inherits))
+#  define IGRAPH_R_GET_VAR_EX(sym, env, inherits, ifnotfound) \
+    R_getVarEx((sym), (env), (inherits), (ifnotfound))
+#else
+static inline SEXP IGRAPH_R_GET_VAR(SEXP sym, SEXP env, Rboolean inherits) {
+  return inherits ? Rf_findVar(sym, env) : Rf_findVarInFrame(env, sym);
+}
+
+static inline SEXP IGRAPH_R_GET_VAR_EX(SEXP sym, SEXP env, Rboolean inherits, SEXP ifnotfound) {
+  SEXP val = IGRAPH_R_GET_VAR(sym, env, inherits);
+  return val == R_UnboundValue ? ifnotfound : val;
+}
+#endif
+
 /* The following three R_check_... functions must only be called from top-level C code,
  * i.e. in contexts where igraph_error() does NOT return. */
 
@@ -238,14 +254,7 @@ Rx_igraph_safe_eval_result_t Rx_igraph_safe_eval_classify_result(SEXP result) {
 SEXP Rx_igraph_safe_eval_in_env(SEXP expr_call, SEXP rho, Rx_igraph_safe_eval_result_t* result) {
   /* find `identity` function used to capture errors */
   SEXP identity = PROTECT(Rf_install("identity"));
-#if R_VERSION >= R_Version(4, 6, 0)
-  SEXP identity_func = PROTECT(R_getVar(identity, R_BaseNamespace, TRUE));
-#else
   SEXP identity_func = PROTECT(Rf_findFun(identity, R_BaseNamespace));
-  if (identity_func == R_UnboundValue) {
-    Rf_error("Failed to find 'base::identity()'");
-  }
-#endif
 
   /* define the call -- enclose with `tryCatch` so we can record errors */
   SEXP try_catch = PROTECT(Rf_install("tryCatch"));
@@ -2415,55 +2424,39 @@ igraph_error_t Rx_igraph_progress_handler(const char *message, double percent,
                               void * data) {
   SEXP ec;
   int ecint;
-  int px = 0;
-  SEXP rho;
-#if R_VERSION >= R_Version(4, 6, 0)
-  rho = R_getRegisteredNamespace("igraph");
-#else
-  SEXP l1 = PROTECT(Rf_install("getNamespace")); px++;
-  SEXP l2 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar("igraph")))); px += 2;
-  SEXP l3 = PROTECT(Rf_lang2(l1, l2)); px++;
-  rho = PROTECT(Rf_eval(l3, R_BaseEnv)); px++;
-#endif
+  SEXP l1 = PROTECT(Rf_install("getNamespace"));
+  SEXP l2 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar("igraph"))));
+  SEXP l3 = PROTECT(Rf_lang2(l1, l2));
+  SEXP rho = PROTECT(Rf_eval(l3, R_BaseEnv));
 
-  SEXP l4 = PROTECT(Rf_install(".igraph.progress")); px++;
-  SEXP l5 = PROTECT(Rf_ScalarReal(percent)); px++;
-  SEXP l6 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar(message)))); px += 2;
-  SEXP l7 = PROTECT(Rf_lang3(l4, l5, l6)); px++;
-  PROTECT(ec=Rf_eval(l7, rho)); px++;
+  SEXP l4 = PROTECT(Rf_install(".igraph.progress"));
+  SEXP l5 = PROTECT(Rf_ScalarReal(percent));
+  SEXP l6 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar(message))));
+  SEXP l7 = PROTECT(Rf_lang3(l4, l5, l6));
+  PROTECT(ec=Rf_eval(l7, rho));
 
   ecint=INTEGER(ec)[0];
-  UNPROTECT(px);
+  UNPROTECT(11);
   return ecint;
 }
 
 igraph_error_t Rx_igraph_status_handler(const char *message, void *data) {
-  int px = 0;
-  SEXP rho;
-#if R_VERSION >= R_Version(4, 6, 0)
-  rho = R_getRegisteredNamespace("igraph");
-#else
-  SEXP l1 = PROTECT(Rf_install("getNamespace")); px++;
-  SEXP l2 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar("igraph")))); px += 2;
-  SEXP l3 = PROTECT(Rf_lang2(l1, l2)); px++;
-  rho = PROTECT(Rf_eval(l3, R_BaseEnv)); px++;
-#endif
+  SEXP l1 = PROTECT(Rf_install("getNamespace"));
+  SEXP l2 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar("igraph"))));
+  SEXP l3 = PROTECT(Rf_lang2(l1, l2));
+  SEXP rho = PROTECT(Rf_eval(l3, R_BaseEnv));
 
-  SEXP l4 = PROTECT(Rf_install(".igraph.status")); px++;
-  SEXP l5 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar(message)))); px += 2;
-  SEXP l6 = PROTECT(Rf_lang2(l4, l5)); px++;
-  PROTECT(Rf_eval(l6, rho)); px++;
+  SEXP l4 = PROTECT(Rf_install(".igraph.status"));
+  SEXP l5 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar(message))));
+  SEXP l6 = PROTECT(Rf_lang2(l4, l5));
+  PROTECT(Rf_eval(l6, rho));
 
-  UNPROTECT(px);
+  UNPROTECT(10);
   return 0;
 }
 
 static R_xlen_t Rx_igraph_altrep_length(SEXP vec) {
-#if R_VERSION >= R_Version(4, 6, 0)
-  SEXP xp=R_getVar(Rf_install("igraph"), R_altrep_data1(vec), TRUE);
-#else
-  SEXP xp=Rf_findVar(Rf_install("igraph"), R_altrep_data1(vec));
-#endif
+  SEXP xp=IGRAPH_R_GET_VAR(Rf_install("igraph"), R_altrep_data1(vec), TRUE);
   igraph_t *g=(igraph_t*)(R_ExternalPtrAddr(xp));
   return igraph_ecount(g);
 }
@@ -2472,11 +2465,7 @@ static void *Rx_igraph_altrep_from(SEXP vec, Rboolean writeable) {
   SEXP data=R_altrep_data2(vec);
   if (data == R_NilValue) {
     Rx_igraph_status_handler("Materializing 'from' vector.\n", NULL);
-#if R_VERSION >= R_Version(4, 6, 0)
-    SEXP xp=R_getVar(Rf_install("igraph"), R_altrep_data1(vec), TRUE);
-#else
-    SEXP xp=Rf_findVar(Rf_install("igraph"), R_altrep_data1(vec));
-#endif
+    SEXP xp=IGRAPH_R_GET_VAR(Rf_install("igraph"), R_altrep_data1(vec), TRUE);
     igraph_t *g=(igraph_t*)(R_ExternalPtrAddr(xp));
 
     data=Ry_igraph_vector_int_to_SEXP(&g->from);
@@ -2491,11 +2480,7 @@ static void *Rx_igraph_altrep_to(SEXP vec, Rboolean writeable) {
   if (data == R_NilValue) {
     Rx_igraph_status_handler("Materializing 'to' vector.\n", NULL);
 
-#if R_VERSION >= R_Version(4, 6, 0)
-    SEXP xp=R_getVar(Rf_install("igraph"), R_altrep_data1(vec), TRUE);
-#else
-    SEXP xp=Rf_findVar(Rf_install("igraph"), R_altrep_data1(vec));
-#endif
+    SEXP xp=IGRAPH_R_GET_VAR(Rf_install("igraph"), R_altrep_data1(vec), TRUE);
     igraph_t *g=(igraph_t*)(R_ExternalPtrAddr(xp));
 
     data=Ry_igraph_vector_int_to_SEXP(&g->to);
@@ -2542,24 +2527,18 @@ SEXP Rx_igraph_set_verbose(SEXP verbose) {
 
 SEXP R_igraph_finalizer(void) {
   IGRAPH_FINALLY_FREE();
-  int px = 0;
-  SEXP rho;
-#if R_VERSION >= R_Version(4, 6, 0)
-  rho = R_getRegisteredNamespace("igraph");
-#else
-  SEXP l1 = PROTECT(Rf_install("getNamespace")); px++;
-  SEXP l2 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar("igraph")))); px += 2;
-  SEXP l3 = PROTECT(Rf_lang2(l1, l2)); px++;
-  rho = PROTECT(Rf_eval(l3, R_BaseEnv)); px++;
-#endif
-
-  SEXP l4 = PROTECT(Rf_install(".igraph.progress")); px++;
-  SEXP l5 = PROTECT(Rf_ScalarReal(0.0)); px++;
-  SEXP l6 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar("")))); px += 2;
-  SEXP l7 = PROTECT(Rf_ScalarLogical(1)); px++;
-  SEXP l8 = PROTECT(Rf_lang4(l4, l5, l6, l7)); px++;
+  SEXP l1 = PROTECT(Rf_install("getNamespace"));
+  SEXP l2 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar("igraph"))));
+  SEXP l3 = PROTECT(Rf_lang2(l1, l2));
+  SEXP rho = PROTECT(Rf_eval(l3, R_BaseEnv));
+
+  SEXP l4 = PROTECT(Rf_install(".igraph.progress"));
+  SEXP l5 = PROTECT(Rf_ScalarReal(0.0));
+  SEXP l6 = PROTECT(Rf_ScalarString(PROTECT(Rf_mkChar(""))));
+  SEXP l7 = PROTECT(Rf_ScalarLogical(1));
+  SEXP l8 = PROTECT(Rf_lang4(l4, l5, l6, l7));
   Rf_eval(l8, rho);
-  UNPROTECT(px);
+  UNPROTECT(11);
   return R_NilValue;
 }
 
@@ -2907,29 +2886,17 @@ igraph_t *Rx_igraph_get_pointer(SEXP graph) {
     Rf_error("This graph was created by a now unsupported old igraph version.\n  Call upgrade_graph() before using igraph functions on that object.");
   }
 
-#if R_VERSION >= R_Version(4, 6, 0)
-  SEXP xp=R_getVarEx(Rf_install("igraph"), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
+  SEXP xp=IGRAPH_R_GET_VAR_EX(Rf_install("igraph"), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
   if (xp == R_NilValue) {
     Rx_igraph_restore_pointer(graph);
-    xp=R_getVarEx(Rf_install("igraph"), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
-  }
-#else
-  SEXP xp=Rf_findVar(Rf_install("igraph"), Rx_igraph_graph_env(graph));
-  if (xp == R_UnboundValue || xp == R_NilValue) {
-    Rx_igraph_restore_pointer(graph);
-    xp=Rf_findVar(Rf_install("igraph"), Rx_igraph_graph_env(graph));
+    xp=IGRAPH_R_GET_VAR_EX(Rf_install("igraph"), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
   }
-#endif
 
   igraph_t *pgraph=(igraph_t*)(R_ExternalPtrAddr(xp));
 
   if (!pgraph) {
     Rx_igraph_restore_pointer(graph);
-#if R_VERSION >= R_Version(4, 6, 0)
-    xp=R_getVarEx(Rf_install("igraph"), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
-#else
-    xp=Rf_findVar(Rf_install("igraph"), Rx_igraph_graph_env(graph));
-#endif
+    xp=IGRAPH_R_GET_VAR_EX(Rf_install("igraph"), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
     pgraph=(igraph_t*)(R_ExternalPtrAddr(xp));
   }
 
@@ -7753,17 +7720,10 @@ SEXP Rx_igraph_graph_version(SEXP graph) {
     return Rf_ScalarInteger(ver_0_4);
   }
 
-#if R_VERSION >= R_Version(4, 6, 0)
-  SEXP ver = R_getVarEx(Rf_install(R_IGRAPH_VERSION_VAR), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
+  SEXP ver = IGRAPH_R_GET_VAR_EX(Rf_install(R_IGRAPH_VERSION_VAR), Rx_igraph_graph_env(graph), TRUE, R_NilValue);
   if (ver == R_NilValue) {
     return Rf_ScalarInteger(ver_0_7_999);
   }
-#else
-  SEXP ver = Rf_findVar(Rf_install(R_IGRAPH_VERSION_VAR), Rx_igraph_graph_env(graph));
-  if (ver == R_UnboundValue) {
-    return Rf_ScalarInteger(ver_0_7_999);
-  }
-#endif
 
   if (TYPEOF(ver) == STRSXP) {
     return Rf_ScalarInteger(ver_0_8);
@@ -7797,6 +7757,7 @@ SEXP Rx_igraph_add_version_to_env(SEXP graph) {
 
 SEXP Rx_igraph_add_env(SEXP graph) {
   SEXP result = graph;
+  R_xlen_t i;
   uuid_t my_id;
   char my_id_chr[40];
   int px = 0;
@@ -7831,11 +7792,7 @@ SEXP Rx_igraph_add_env(SEXP graph) {
 }
 
 SEXP Rx_igraph_get_graph_id(SEXP graph) {
-#if R_VERSION >= R_Version(4, 6, 0)
-  return R_getVar(Rf_install("myid"), Rx_igraph_graph_env(graph), TRUE);
-#else
-  return Rf_findVar(Rf_install("myid"), Rx_igraph_graph_env(graph));
-#endif
+  return IGRAPH_R_GET_VAR(Rf_install("myid"), Rx_igraph_graph_env(graph), TRUE);
 }
 
 // Wrapper functions for functions not in aaa-auto.R