diff --git a/src/shell/shell_misc.cpp b/src/shell/shell_misc.cpp
index 8575eb12..8723014e 100644
--- a/src/shell/shell_misc.cpp
+++ b/src/shell/shell_misc.cpp
@@ -253,17 +253,21 @@ void DOS_Shell::InputCommand(char * line) {
 					if ((path = strrchr(line+completion_index,'/'))) completion_index = (Bit16u)(path-line+1);
 
 					// build the completion list
-					char mask[DOS_PATHLENGTH];
+					char mask[DOS_PATHLENGTH] = {0};
+					if (strlen(p_completion_start) + 3 >= DOS_PATHLENGTH) {
+						//Beep;
+						break;
+					}
 					if (p_completion_start) {
-						strcpy(mask, p_completion_start);
+						safe_strncpy(mask, p_completion_start,DOS_PATHLENGTH);
 						char* dot_pos=strrchr(mask,'.');
 						char* bs_pos=strrchr(mask,'\\');
 						char* fs_pos=strrchr(mask,'/');
 						char* cl_pos=strrchr(mask,':');
 						// not perfect when line already contains wildcards, but works
 						if ((dot_pos-bs_pos>0) && (dot_pos-fs_pos>0) && (dot_pos-cl_pos>0))
-							strcat(mask, "*");
-						else strcat(mask, "*.*");
+							strncat(mask, "*",DOS_PATHLENGTH - 1);
+						else strncat(mask, "*.*",DOS_PATHLENGTH - 1);
 					} else {
 						strcpy(mask, "*.*");
 					}