diff --git a/ChangeLog b/ChangeLog
index 1804037f3..bb619cf49 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,8 @@
 
 	* 52516: Src/prompt.c: fix crash in %H when hlgroups is empty
 
+	* 52517: Src/prompt.c: ensure that %H is followed by {
+
 2024-02-03  Bart Schaefer  <schaefer@zsh.org>
 
 	* unposted: Util/printdefines: updates and fix omissions
diff --git a/Src/prompt.c b/Src/prompt.c
index b1e5041bd..0d674ceab 100644
--- a/Src/prompt.c
+++ b/Src/prompt.c
@@ -605,10 +605,12 @@ putpromptchar(int doprint, int endchar)
 	        applytextattributes(TSC_PROMPT);
 		break;
 	    case 'H':
-		bv->fm = parsehighlight(bv->fm + 2, '}', &atr);
-		if (atr != TXT_ERROR) {
-		    treplaceattrs(atr);
-		    applytextattributes(TSC_PROMPT);
+		if (bv->fm[1] == '{') {
+		    bv->fm = parsehighlight(bv->fm + 2, '}', &atr);
+		    if (atr != TXT_ERROR) {
+			treplaceattrs(atr);
+			applytextattributes(TSC_PROMPT);
+		    }
 		}
 		break;
 	    case '[':