diff --git a/core/wasm_shims/tooldata/tooldata_runtime_stubs.cc b/core/wasm_shims/tooldata/tooldata_runtime_stubs.cc
index e2be052..04223e7 100644
--- a/core/wasm_shims/tooldata/tooldata_runtime_stubs.cc
+++ b/core/wasm_shims/tooldata/tooldata_runtime_stubs.cc
@@ -1,5 +1,6 @@
 #include "tooldata.hh"
 
+#include <cstdio>
 #include <cstring>
 #include <unistd.h>
 
@@ -15,7 +16,11 @@ bool db_live = false;
 extern "C" {
 
 int tool_nml_register(CANON_TOOL_TABLE *tblptr) {
-    return tblptr ? 0 : -1;
+    if (!tblptr) {
+        std::fprintf(stderr, "%5d!!!PROBLEM tool_nml_register()\n", getpid());
+        return -1;
+    }
+    return 0;
 }
 
 int tooldata_db_init(char progname_plus_args[], int) {
@@ -29,10 +34,14 @@ int tooldata_db_init(char progname_plus_args[], int) {
     for (char *token = program; token; token = strtok_r(nullptr, " ", &saveptr)) {
         ++argc;
         if (argc >= MAX_DB_PROGRAM_ARGS) {
+            std::fprintf(stderr,
+                         "!!!!db_init: argc exceeds MAX_DB_PROGRAM_ARGS=%d\n",
+                         MAX_DB_PROGRAM_ARGS);
             return -1;
         }
     }
     if (!program || access(program, X_OK) != 0) {
+        std::fprintf(stderr, "!!!!db_init: <%s> not executable\n", program ? program : "");
         return -1;
     }
     return -1;
diff --git a/test-linuxcnc-wasm-tooldata-link.sh b/test-linuxcnc-wasm-tooldata-link.sh
index 9c1feb4..1db5906 100755
--- a/test-linuxcnc-wasm-tooldata-link.sh
+++ b/test-linuxcnc-wasm-tooldata-link.sh
@@ -11,5 +11,9 @@ probe=$(./build-linuxcnc-wasm-standalone-probe.sh --mode tooldata-link)
 "$probe" 2>"$probe.err"
 grep -F "tool_mmap_user(): tool mmap not available" "$probe.err" >/dev/null
 grep -F "tooldata_put() no tool_mmap_base" "$probe.err" >/dev/null
+grep -F "!!!PROBLEM tool_nml_register()" "$probe.err" >/dev/null
+grep -F "!!!!db_init: <" "$probe.err" >/dev/null
+grep -F "not executable" "$probe.err" >/dev/null
+grep -F "!!!!db_init: argc exceeds MAX_DB_PROGRAM_ARGS=10" "$probe.err" >/dev/null
 
 echo "linuxcnc wasm tooldata shim link probe passed"