diff --git a/src/common.cpp b/src/common.cpp
index 08b86b9c9..541d976bc 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -1975,13 +1975,3 @@ bool is_console_session() {
     return console_session;
 }
 
-static_assert(const_strcmp("", "a") < 0, "const_strcmp failure");
-static_assert(const_strcmp("a", "a") == 0, "const_strcmp failure");
-static_assert(const_strcmp("a", "") > 0, "const_strcmp failure");
-static_assert(const_strcmp("aa", "a") > 0, "const_strcmp failure");
-static_assert(const_strcmp("a", "aa") < 0, "const_strcmp failure");
-static_assert(const_strcmp("b", "aa") > 0, "const_strcmp failure");
-
-static_assert(const_strlen("") == 0, "const_strlen failure");
-static_assert(const_strlen("a") == 1, "const_strlen failure");
-static_assert(const_strlen("hello") == 5, "const_strlen failure");
diff --git a/src/common.h b/src/common.h
index d5a2c9495..8bb92a3b0 100644
--- a/src/common.h
+++ b/src/common.h
@@ -701,19 +701,13 @@ constexpr ssize_t const_strcmp(const T *lhs, const T *rhs) {
 
 /// Compile-time agnostic-size strlen/wcslen implementation. Unicode-unaware.
 template <typename T, size_t N>
-constexpr size_t const_strlen(const T (&val)[N], ssize_t index = -1) {
-    // N is the length of the character array, but that includes one **or more** trailing nuls.
-    static_assert(N > 0, "Invalid input to const_strlen");
-    return index == -1
-               ?
-               // Assume a minimum of one trailing nul and do a quick check for the usual case
-               // (single trailing nul) before recursing:
-               N - 1 - (N <= 2 || val[N - 2] != static_cast<T>(0) ? 0 : const_strlen(val, N - 2))
-               // Prevent an underflow in case the string is comprised of all \0 bytes
-               : index == 0
-                     ? 0
-                     // Keep back-tracking until a non-nul byte is found
-                     : (val[index] != static_cast<T>(0) ? 0 : 1 + const_strlen(val, index - 1));
+constexpr size_t const_strlen(const T (&val)[N], size_t last_checked_idx = N,
+                              size_t first_nul_idx = N) {
+    // Assume there's a nul char at the end (index N) but there may be one before that that.
+    return last_checked_idx == 0
+               ? first_nul_idx
+               : const_strlen(val, last_checked_idx - 1,
+                              val[last_checked_idx - 1] ? first_nul_idx : last_checked_idx - 1);
 }
 
 /// Compile-time assertion of alphabetical sort of array `array`, by specified
diff --git a/src/fish_tests.cpp b/src/fish_tests.cpp
index f26f8abde..94ea9d56b 100644
--- a/src/fish_tests.cpp
+++ b/src/fish_tests.cpp
@@ -1671,10 +1671,39 @@ static void test_wcsfilecmp() {
     }
 }
 
+static void test_const_strlen() {
+    do_test(const_strlen("") == 0);
+    do_test(const_strlen(L"") == 0);
+    do_test(const_strlen("\0") == 0);
+    do_test(const_strlen(L"\0") == 0);
+    do_test(const_strlen("\0abc") == 0);
+    do_test(const_strlen(L"\0abc") == 0);
+    do_test(const_strlen("x") == 1);
+    do_test(const_strlen(L"x") == 1);
+    do_test(const_strlen("abc") == 3);
+    do_test(const_strlen(L"abc") == 3);
+    do_test(const_strlen("abc\0def") == 3);
+    do_test(const_strlen(L"abc\0def") == 3);
+    do_test(const_strlen("abcdef\0") == 6);
+    do_test(const_strlen(L"abcdef\0") == 6);
+    static_assert(const_strlen("hello") == 5, "const_strlen failure");
+}
+
+static void test_const_strcmp() {
+    static_assert(const_strcmp("", "a") < 0, "const_strcmp failure");
+    static_assert(const_strcmp("a", "a") == 0, "const_strcmp failure");
+    static_assert(const_strcmp("a", "") > 0, "const_strcmp failure");
+    static_assert(const_strcmp("aa", "a") > 0, "const_strcmp failure");
+    static_assert(const_strcmp("a", "aa") < 0, "const_strcmp failure");
+    static_assert(const_strcmp("b", "aa") > 0, "const_strcmp failure");
+}
+
 static void test_utility_functions() {
     say(L"Testing utility functions");
     test_wcsfilecmp();
     test_parse_util_cmdsubst_extent();
+    test_const_strlen();
+    test_const_strcmp();
 }
 
 // UTF8 tests taken from Alexey Vatchenko's utf8 library. See http://www.bsdua.org/libbsdua.html.