diff --git a/src/cmd/ksh93/edit/completion.c b/src/cmd/ksh93/edit/completion.c
index fe9261583..7125373da 100644
--- a/src/cmd/ksh93/edit/completion.c
+++ b/src/cmd/ksh93/edit/completion.c
@@ -173,10 +173,16 @@ static char *find_begin(char outbuff[], char *last, int endchar, int *type)
 				xp = find_begin(cp,last,')',type);
 				if(*(cp=xp)!=')')
 					bp = xp;
-				else
-					cp++;
 			}
 			break;
+		    case '`':
+			if(inquote=='\'')
+				break;
+			*type = mode;
+			xp = find_begin(cp,last,'`',type);
+			if(*(cp=xp)!='`')
+				bp = xp;
+			break;
 		    case '=':
 			if(!inquote)
 			{
@@ -447,9 +453,9 @@ int ed_expand(Edit_t *ep, char outbuff[],int *cur,int *eol,int mode, int count)
 					out = overlaid(begin,*com++,nocase);
 			}
 			mode = (out==saveout);
-			if(out[-1]==0)
+			if(out>outbuff && out[-1]==0)
 				out--;
-			if(mode && out[-1]!='/')
+			if(mode && (out==outbuff || out>outbuff && out[-1]!='/'))
 			{
 				if(cmd_completion)
 				{
diff --git a/src/cmd/ksh93/tests/pty.sh b/src/cmd/ksh93/tests/pty.sh
index 7d5f0c317..ddf45ddee 100755
--- a/src/cmd/ksh93/tests/pty.sh
+++ b/src/cmd/ksh93/tests/pty.sh
@@ -858,5 +858,19 @@ w test \$\{.sh.level\t
 r ^:test-1: test \$\{.sh.level\}\r\n$
 !
 
+# err_exit #
+((SHOPT_VSH || SHOPT_ESH)) && tst $LINENO <<"!"
+L tab completion executes command substitutions
+# https://github.com/ksh93/ksh/issues/268
+
+d 15
+p :test-1:
+w $(echo true)\t
+r ^:test-1: \$\(echo true\)\r\n$
+p :test-2:
+w `echo true`\t
+r ^:test-2: `echo true`\r\n$
+!
+
 # ======
 exit $((Errors<125?Errors:125))