diff --git a/src/errors.h b/src/errors.h
index 8a2461b..b4cf8ae 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -446,3 +446,5 @@
 	INIT(= N_("E1200: Decryption failed!"));
 EXTERN char e_libsodium_decryption_failed_premature[]
 	INIT(= N_("E1201: Decryption failed: pre-mature end of file!"));
+EXTERN char e_no_white_space_allowed_after_str_str[]
+	INIT(= N_("E1202: No white space allowed after '%s': %s"));
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index a26867f..cba7972 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -1906,6 +1906,12 @@
       unlet g:count
   END
   CheckDefAndScriptSuccess(lines)
+
+  lines =<< trim END
+      var nr = 7
+      ++ nr
+  END
+  CheckDefAndScriptFailure(lines, "E1202: No white space allowed after '++': ++ nr")
 enddef
 
 
diff --git a/src/version.c b/src/version.c
index 3898725..4cef712 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3048,
+/**/
     3047,
 /**/
     3046,
diff --git a/src/vim9compile.c b/src/vim9compile.c
index e78a032..cd83aea 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -6639,6 +6639,12 @@
     }
     if (eap->cmdidx == CMD_increment || eap->cmdidx == CMD_decrement)
     {
+	if (VIM_ISWHITE(eap->cmd[2]))
+	{
+	    semsg(_(e_no_white_space_allowed_after_str_str),
+			 eap->cmdidx == CMD_increment ? "++" : "--", eap->cmd);
+	    return NULL;
+	}
 	op = (char_u *)(eap->cmdidx == CMD_increment ? "+=" : "-=");
 	oplen = 2;
 	incdec = TRUE;
diff --git a/src/vim9script.c b/src/vim9script.c
index 7c6526b..9dc67a7 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -169,6 +169,13 @@
     char_u	*nextcmd = eap->nextcmd;
     size_t	len = STRLEN(eap->cmd) + 8;
 
+    if (VIM_ISWHITE(cmd[2]))
+    {
+	semsg(_(e_no_white_space_allowed_after_str_str),
+			 eap->cmdidx == CMD_increment ? "++" : "--", eap->cmd);
+	return;
+    }
+
     // This works like "nr += 1" or "nr -= 1".
     // Add a '|' to avoid looking in the next line.
     eap->cmd = alloc(len);