diff --git a/include/string.h b/include/string.h
index abaf80e7d..b19f44e31 100644
--- a/include/string.h
+++ b/include/string.h
@@ -81,6 +81,7 @@ void __fastcall__ bzero (void* ptr, size_t n);                /* BSD */
 char* __fastcall__ strdup (const char* s);                    /* SYSV/BSD */
 int __fastcall__ stricmp (const char* s1, const char* s2);    /* DOS/Windows */
 int __fastcall__ strcasecmp (const char* s1, const char* s2); /* Same for Unix */
+char* __fastcall__ strcasestr (const char* str, const char* substr);
 int __fastcall__ strnicmp (const char* s1, const char* s2, size_t count);     /* DOS/Windows */
 int __fastcall__ strncasecmp (const char* s1, const char* s2, size_t count);  /* Same for Unix */
 size_t __fastcall__ strnlen (const char* s, size_t maxlen);     /* POSIX.1-2008 */
diff --git a/libsrc/common/strcasestr.c b/libsrc/common/strcasestr.c
new file mode 100644
index 000000000..693b43a37
--- /dev/null
+++ b/libsrc/common/strcasestr.c
@@ -0,0 +1,36 @@
+/*
+** strcasestr.c
+**
+** Colin Leroy-Mira, 2024
+*/
+
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+
+/*****************************************************************************/
+/*                                   Code                                    */
+/*****************************************************************************/
+
+
+
+char* __fastcall__ strcasestr(const char *str, const char *substr) {
+  size_t len_a = strlen(str);
+  size_t len_b = strlen(substr);
+  const char *end_str;
+
+  if (len_a < len_b)
+    return NULL;
+
+  len_a -= len_b;
+
+  for (end_str = str + len_a + 1; str < end_str; str++) {
+    if (!strncasecmp(str, substr, len_b))
+      return (char *)str;
+  }
+  return NULL;
+}
diff --git a/test/val/strstr-test.c b/test/val/strstr-test.c
new file mode 100644
index 000000000..5c8a147b0
--- /dev/null
+++ b/test/val/strstr-test.c
@@ -0,0 +1,41 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+int fails = 0;
+
+#define STRSTR_TEST(needle,expected)                     \
+  if (strstr(haystack, (needle)) != (expected)) {        \
+    printf("strstr failure: expected %p for \"%s\", "    \
+           "got %p\n",                                   \
+           expected, needle, strstr(haystack, (needle)));\
+    fails++;                                             \
+  }
+
+#define STRCASESTR_TEST(needle,expected)                     \
+  if (strcasestr(haystack, (needle)) != (expected)) {        \
+    printf("strcasestr failure: expected %p for \"%s\", "    \
+           "got %p\n",                                       \
+           expected, needle, strcasestr(haystack, (needle)));\
+    fails++;                                                 \
+  }
+
+int main (void)
+{
+    const char *haystack = "This is a string to search in";
+
+    STRSTR_TEST("This is", haystack + 0);
+    STRSTR_TEST("a string", haystack + 8);
+    STRSTR_TEST("This is a string to search in", haystack);
+    STRSTR_TEST("search in", haystack + 20);
+    STRSTR_TEST("This is a string to search in with extra chars", NULL);
+    STRSTR_TEST("nowhere", NULL);
+
+    STRCASESTR_TEST("this is", haystack + 0);
+    STRCASESTR_TEST("a STRING", haystack + 8);
+    STRCASESTR_TEST("this is a string TO search in", haystack);
+    STRCASESTR_TEST("This is a string to search in with extra chars", NULL);
+    STRCASESTR_TEST("search IN", haystack + 20);
+
+    return fails;
+}