diff --git a/src/symbol_table.c b/src/symbol_table.c
index ce69570..2204ba3 100644
--- a/src/symbol_table.c
+++ b/src/symbol_table.c
@@ -528,13 +528,13 @@ TableNode *getReturn(TableNode *definition) {
         printdebug(
             "passed a NULL entry to getReturn "
             "function. Invalid.");
-        return NULL;
+        return undefined;
     }
     if (definition == undefined) {
         printdebug(
             "passed an undefined entry to getReturn "
             "function. Invalid.");
-        return NULL;
+        return undefined;
     }
     if (strcmp(getType(definition), "primitive function type") != 0) {
         printdebug(