diff --git a/src/grib_accessor_class_ascii.c b/src/grib_accessor_class_ascii.c
index aae484dc3..6ec67e107 100644
--- a/src/grib_accessor_class_ascii.c
+++ b/src/grib_accessor_class_ascii.c
@@ -245,6 +245,7 @@ static int unpack_double (grib_accessor* a, double*v, size_t *len)
     char val[1024];
     size_t l = sizeof(val);
     char  *last = NULL;
+
     grib_unpack_string (a , val, &l);
 
     *v = strtod(val,&last);
@@ -255,7 +256,8 @@ static int unpack_double (grib_accessor* a, double*v, size_t *len)
         return GRIB_SUCCESS;
     }
 
-    grib_context_log(a->context,GRIB_LOG_ERROR,"Cannot unpack %s as double",a->name);
+    grib_context_log(a->context,GRIB_LOG_ERROR,"Cannot unpack %s as double. Hint: Try unpacking as string",a->name);
+
     return GRIB_NOT_IMPLEMENTED;
 }
 
diff --git a/src/grib_accessor_class_concept.c b/src/grib_accessor_class_concept.c
index 37ccd7c93..bfe681ed1 100644
--- a/src/grib_accessor_class_concept.c
+++ b/src/grib_accessor_class_concept.c
@@ -463,6 +463,7 @@ static long get_ECMWF_local_paramId(grib_accessor* a, grib_handle* h)
 
 static int unpack_long(grib_accessor* a, long* val, size_t *len)
 {
+    char *endptr;
     const char *p = concept_evaluate(a);
 
     if(!p) {
@@ -480,8 +481,16 @@ static int unpack_long(grib_accessor* a, long* val, size_t *len)
         return GRIB_NOT_FOUND;
     }
 
-    *val = atol(p);
     *len = 1;
+    *val = strtol(p, &endptr, 10);
+    if (endptr == p) {
+        int type = GRIB_TYPE_UNDEFINED;
+        grib_context_log(a->context,GRIB_LOG_ERROR,"Cannot unpack %s as long",a->name);
+        if (grib_get_native_type(grib_handle_of_accessor(a), a->name, &type) == GRIB_SUCCESS) {
+            grib_context_log(a->context,GRIB_LOG_ERROR,"Hint: Try unpacking as %s", grib_get_type_name(type));
+        }
+        return GRIB_DECODING_ERROR;
+    }
 
     return GRIB_SUCCESS;
 }
diff --git a/src/grib_accessor_class_gen.c b/src/grib_accessor_class_gen.c
index d227e8db9..92c5c2a8e 100644
--- a/src/grib_accessor_class_gen.c
+++ b/src/grib_accessor_class_gen.c
@@ -268,6 +268,7 @@ static int clear(grib_accessor* a)
 
 static int  unpack_long   (grib_accessor* a, long*  v, size_t *len)
 {
+    int type = GRIB_TYPE_UNDEFINED;
     if(a->cclass->unpack_double && a->cclass->unpack_double != &unpack_double)
     {
         double val = 0.0;
@@ -295,11 +296,15 @@ static int  unpack_long   (grib_accessor* a, long*  v, size_t *len)
     }
 
     grib_context_log(a->context,GRIB_LOG_ERROR,"Cannot unpack %s as long",a->name);
+    if (grib_get_native_type(grib_handle_of_accessor(a), a->name, &type) == GRIB_SUCCESS) {
+        grib_context_log(a->context,GRIB_LOG_ERROR,"Hint: Try unpacking as %s", grib_get_type_name(type));
+    }
     return GRIB_NOT_IMPLEMENTED;
 }
 
 static int unpack_double (grib_accessor* a, double*v, size_t *len)
 {
+    int type = GRIB_TYPE_UNDEFINED;
     if(a->cclass->unpack_long && a->cclass->unpack_long != &unpack_long)
     {
         long val = 0;
@@ -327,12 +332,15 @@ static int unpack_double (grib_accessor* a, double*v, size_t *len)
     }
 
     grib_context_log(a->context,GRIB_LOG_ERROR,"Cannot unpack %s as double",a->name);
+    if (grib_get_native_type(grib_handle_of_accessor(a), a->name, &type) == GRIB_SUCCESS) {
+        grib_context_log(a->context,GRIB_LOG_ERROR,"Hint: Try unpacking as %s", grib_get_type_name(type));
+    }
+
     return GRIB_NOT_IMPLEMENTED;
 }
 
 static int unpack_string(grib_accessor*a , char*  v, size_t *len)
 {
-
     if(a->cclass->unpack_double && a->cclass->unpack_double != &unpack_double)
     {
         double val = 0.0;