diff --git a/interop/src/cpp/types/signatures.cc b/interop/src/cpp/types/signatures.cc
index 9e16aa58666ef540d1ba9b4a8fa3206cf736130a..3c7b315dab3dac0c09b2118cf7783b7c633527fd 100644
--- a/interop/src/cpp/types/signatures.cc
+++ b/interop/src/cpp/types/signatures.cc
@@ -78,6 +78,7 @@ std::string sigType(const std::string &type) {
     KOALA_INTEROP_TYPEDEFS("sigType", "jni")
 #endif
     fprintf(stderr, "Unhandled type: %s\n", type.c_str());
+    return type;
 }
 
 std::string codeType(const std::string &type) {
@@ -87,6 +88,7 @@ std::string codeType(const std::string &type) {
     KOALA_INTEROP_TYPEDEFS("codeType", "jni")
 #endif
     fprintf(stderr, "Unhandled type: %s\n", type.c_str());
+    return type;
 }
 
 std::string convertType(const char* name, const char* koalaType) {