diff --git a/src/map/achievement.c b/src/map/achievement.c
index 90b1059a34..dc6c45a516 100644
--- a/src/map/achievement.c
+++ b/src/map/achievement.c
@@ -879,8 +879,8 @@ const char* av_parse_subexpr(const char* p, int limit, struct av_condition *pare
 	p = skip_space(p);
 
 	while((
-			(op=C_ADD,opl=9,len=1,*p=='+') ||
-			(op=C_SUB,opl=9,len=1,*p=='-') ||
+			((op=C_ADD,opl=9,len=1,*p=='+') && p[1]!='+') ||
+			((op=C_SUB,opl=9,len=1,*p=='-') && p[1]!='-') ||
 			(op=C_MUL,opl=10,len=1,*p=='*') ||
 			(op=C_DIV,opl=10,len=1,*p=='/') ||
 			(op=C_MOD,opl=10,len=1,*p=='%') ||