diff --git a/src/dogroups.c b/src/dogroups.c
index 79ace0439..d6195ecd1 100644
--- a/src/dogroups.c
+++ b/src/dogroups.c
@@ -137,7 +137,7 @@ SEXP dogroups(SEXP dt, SEXP dtcols, SEXP groups, SEXP grpcols, SEXP jiscols, SEX
   // using <- in j (which is valid, useful and tested), they are repointed to the .SD cols for each group.
   SEXP names = PROTECT(getAttrib(SDall, R_NamesSymbol)); nprotect++;
   if (length(names) != length(SDall))
-    internal_error("length(names)!=length(SD)");
+    internal_error(__func__, "length(names)!=length(SD)");
   SEXP *nameSyms = (SEXP *)R_alloc(length(names), sizeof(SEXP));
 
   for(int i=0; i<length(SDall); ++i) {
@@ -154,7 +154,7 @@ SEXP dogroups(SEXP dt, SEXP dtcols, SEXP groups, SEXP grpcols, SEXP jiscols, SEX
 
   SEXP xknames = PROTECT(getAttrib(xSD, R_NamesSymbol)); nprotect++;
   if (length(xknames) != length(xSD))
-    internal_error("length(xknames)!=length(xSD)");
+    internal_error(__func__, "length(xknames)!=length(xSD)");
   SEXP *xknameSyms = (SEXP *)R_alloc(length(xknames), sizeof(SEXP));
   for(int i=0; i<length(xSD); ++i) {
     if (SIZEOF(VECTOR_ELT(xSD, i))==0)