diff --git a/w32/subproc/misc.c b/w32/subproc/misc.c
index 96e43aee..5273fa0c 100644
--- a/w32/subproc/misc.c
+++ b/w32/subproc/misc.c
@@ -36,7 +36,7 @@ int _cdecl compare(const void *a1, const void *a2)
         return _stricoll(*((char**)a1),*((char**)a2));
 }
 bool_t
-arr2envblk(char **arr, char **envblk_out)
+arr2envblk(char **arr, char **envblk_out, int *envsize_needed)
 {
         char **tmp;
         int size_needed;
@@ -54,13 +54,14 @@ arr2envblk(char **arr, char **envblk_out)
         }
 
         arrcnt = 0;
-        size_needed = 0;
+        size_needed = *envsize_needed = 0;
         while (arr[arrcnt]) {
                 tmp[arrcnt] = arr[arrcnt];
                 size_needed += strlen(arr[arrcnt]) + 1;
                 arrcnt++;
         }
         size_needed++;
+        *envsize_needed = size_needed;
 
         qsort((void *) tmp, (size_t) arrcnt, sizeof (char*), compare);
 
diff --git a/w32/subproc/proc.h b/w32/subproc/proc.h
index 62ebf65f..2dad3953 100644
--- a/w32/subproc/proc.h
+++ b/w32/subproc/proc.h
@@ -24,6 +24,6 @@ typedef int bool_t;
 #define E_NO_MEM        103
 #define E_FORK          104
 
-extern bool_t arr2envblk(char **arr, char **envblk_out);
+extern bool_t arr2envblk(char **arr, char **envblk_out, int *envsize_needed);
 
 #endif
diff --git a/w32/subproc/sub_proc.c b/w32/subproc/sub_proc.c
index 7cacac67..34cc85d2 100644
--- a/w32/subproc/sub_proc.c
+++ b/w32/subproc/sub_proc.c
@@ -593,6 +593,7 @@ process_begin(
         STARTUPINFO startInfo;
         PROCESS_INFORMATION procInfo;
         char *envblk=NULL;
+        int envsize_needed = 0;
         int pass_null_exec_path = 0;
 
         /*
@@ -734,10 +735,15 @@ process_begin(
         }
 
         if (envp) {
-                if (arr2envblk(envp, &envblk) ==FALSE) {
+                if (arr2envblk(envp, &envblk, &envsize_needed) == FALSE) {
                         pproc->last_err = 0;
                         pproc->lerrno = E_NO_MEM;
                         free( command_line );
+                        if (pproc->last_err == ERROR_INVALID_PARAMETER
+                            && envsize_needed > 32*1024) {
+                                fprintf (stderr, "CreateProcess failed, probably because environment is too large (%d bytes).\n",
+                                         envsize_needed);
+                        }
                         return(-1);
                 }
         }