diff --git a/src/exec.cpp b/src/exec.cpp
index ff84cb698..6268ad199 100644
--- a/src/exec.cpp
+++ b/src/exec.cpp
@@ -92,6 +92,12 @@ static bool is_thompson_shell_payload(const char *p, size_t n) {
 /// such as Actually Portable Executable.
 /// N.B.: this is called after fork, it must not allocate heap memory.
 bool is_thompson_shell_script(const char *path) {
+    // Paths ending in ".fish" are never considered Thompson shell scripts.
+    if (const char *lastdot = strrchr(path, '.')) {
+        if (0 == strcmp(lastdot, ".fish")) {
+            return false;
+        }
+    }
     int e = errno;
     bool res = false;
     int fd = open_cloexec(path, O_RDONLY | O_NOCTTY);
diff --git a/tests/checks/noshebang.fish b/tests/checks/noshebang.fish
index c58111144..c5353fed1 100644
--- a/tests/checks/noshebang.fish
+++ b/tests/checks/noshebang.fish
@@ -32,6 +32,27 @@ runfile
 #CHECK: 0
 #CHECK: 0
 
+# Never implicitly pass files ending with .fish to /bin/sh.
+true >file.fish
+chmod a+x file.fish
+set -g fish_use_posix_spawn 0
+./file.fish
+echo $status
+set -g fish_use_posix_spawn 1
+./file.fish
+echo $status
+rm file.fish
+#CHECK: 125
+#CHECKERR: Failed {{.*}}
+#CHECKERR: exec: {{.*}}
+#CHECKERR: {{.*}}
+
+#CHECK: 125
+#CHECKERR: Failed {{.*}}
+#CHECKERR: exec: {{.*}}
+#CHECKERR: {{.*}}
+
+
 # On to NUL bytes.
 # The heuristic is that there must be a line containing a lowercase letter before the first NUL byte.
 echo -n -e 'true\n\x00' >file