diff --git a/src/rinterface.c b/src/rinterface.c
index 73f43d321a..c32b4ac71a 100644
--- a/src/rinterface.c
+++ b/src/rinterface.c
@@ -10735,7 +10735,12 @@ SEXP R_igraph_almost_equals(SEXP a, SEXP b, SEXP eps) {
   igraph_bool_t c_result;
   SEXP r_result;
                                         /* Convert input */
-
+  IGRAPH_R_CHECK_REAL(a);
+  c_a = REAL(a)[0];
+  IGRAPH_R_CHECK_REAL(b);
+  c_b = REAL(b)[0];
+  IGRAPH_R_CHECK_REAL(eps);
+  c_eps = REAL(eps)[0];
                                         /* Call igraph */
   c_result=igraph_almost_equals(c_a, c_b, c_eps);
 
@@ -10759,7 +10764,12 @@ SEXP R_igraph_cmp_epsilon(SEXP a, SEXP b, SEXP eps) {
   int c_result;
   SEXP r_result;
                                         /* Convert input */
-
+  IGRAPH_R_CHECK_REAL(a);
+  c_a = REAL(a)[0];
+  IGRAPH_R_CHECK_REAL(b);
+  c_b = REAL(b)[0];
+  IGRAPH_R_CHECK_REAL(eps);
+  c_eps = REAL(eps)[0];
                                         /* Call igraph */
   c_result=igraph_cmp_epsilon(c_a, c_b, c_eps);
 
diff --git a/tools/stimulus/types-RC.yaml b/tools/stimulus/types-RC.yaml
index 53cdaaa7d4..777509ecd3 100644
--- a/tools/stimulus/types-RC.yaml
+++ b/tools/stimulus/types-RC.yaml
@@ -76,6 +76,21 @@ CSTRING:
         OUT: |-
             PROTECT(%I% = Rf_mkCharLenCE(%C%, strlen(%C%), CE_UTF8));
 
+DOUBLE:
+    CTYPE: double
+    CALL:
+        IN: '%C%'
+        OUT: '&%C%'
+        INOUT: '&%C%'
+    INCONV:
+        IN: |-
+            IGRAPH_R_CHECK_REAL(%I%);
+            %C% = REAL(%I%)[0];
+    OUTCONV:
+        OUT: |-
+            PROTECT(%I%=NEW_NUMERIC(1));
+            REAL(%I%)[0]=%C%;
+
 REAL:
     CTYPE: igraph_real_t
     CALL: