diff --git a/src/syntax.c b/src/syntax.c
index 9e2971e..ea4e74c 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -8788,9 +8788,9 @@
 		if (spell_aep->ae_u.cterm.bg_color > 0)
 		    new_en.ae_u.cterm.bg_color = spell_aep->ae_u.cterm.bg_color;
 #ifdef FEAT_TERMTRUECOLOR
-		if (spell_aep->ae_u.cterm.fg_rgb != INVALCOLOR)
+		if (spell_aep->ae_u.cterm.fg_rgb != (long_u)INVALCOLOR)
 		    new_en.ae_u.cterm.fg_rgb = spell_aep->ae_u.cterm.fg_rgb;
-		if (spell_aep->ae_u.cterm.bg_rgb != INVALCOLOR)
+		if (spell_aep->ae_u.cterm.bg_rgb != (long_u)INVALCOLOR)
 		    new_en.ae_u.cterm.bg_rgb = spell_aep->ae_u.cterm.bg_rgb;
 #endif
 	    }