diff --git a/bypy/linux/launcher.c b/bypy/linux/launcher.c
index fc9cbbf7c6..77088353c3 100644
--- a/bypy/linux/launcher.c
+++ b/bypy/linux/launcher.c
@@ -26,16 +26,21 @@ int main(int argc, char **argv) {
     }
     strncpy(lib, buf, PATHLEN);
     strncpy(base, dirname(lib), PATHLEN);
-    snprintf(exe, PATHLEN, "%s/bin/%s", base, basename(buf));
+    int ret = snprintf(exe, PATHLEN, "%s/bin/%s", base, basename(buf));
+    if (ret < 0 || ret > (PATHLEN-2)) { fprintf(stderr, "Path to executable too long: %s/bin/%s", base, basename(buf)); return 1; }
     memset(lib, 0, PATHLEN);
-    snprintf(lib, PATHLEN, "%s/lib", base);
+    ret = snprintf(lib, PATHLEN, "%s/lib", base);
+    if (ret < 0 || ret > (PATHLEN-2)) { fprintf(stderr, "Path to lib too long: %s/lib", base); return 1; }
 
     SET("CALIBRE_QT_PREFIX", base)
 
     memset(buf, 0, PATHLEN);
     ldp = getenv("LD_LIBRARY_PATH");
     if (ldp == NULL) strncpy(buf, lib, PATHLEN);
-    else snprintf(buf, PATHLEN, "%s:%s", lib, ldp);
+    else {
+        ret = snprintf(buf, PATHLEN, "%s:%s", lib, ldp);
+        if (ret < 0 || ret > (PATHLEN-2)) { fprintf(stderr, "LD_LIBRARY_PATH too long: %s:%s", lib, ldp); return 1; }
+    }
     SET("LD_LIBRARY_PATH", buf)
 
     argv[0] = exe;