diff --git a/src/stdlib/src/lib.rs b/src/stdlib/src/lib.rs
index dea8dbd13a4b17def216925f39324048faca1c66..7813b9bdc953c45e9a8a8a173f130f6022c95d4a 100644
--- a/src/stdlib/src/lib.rs
+++ b/src/stdlib/src/lib.rs
@@ -23,8 +23,30 @@ pub const EXIT_SUCCESS: c_int = 0;
 static mut ATEXIT_FUNCS: [Option<extern "C" fn()>; 32] = [None; 32];
 
 #[no_mangle]
-pub extern "C" fn a64l(s: *const c_char) -> c_long {
-    unimplemented!();
+pub unsafe extern "C" fn a64l(s: *const c_char) -> c_long {
+    if s.is_null() {
+        return 0;
+    }
+    let mut l: c_long = 0;
+    // a64l does not support more than 6 characters at once
+    for x in 0..6 {
+        let c = *s.offset(x);
+        if c == 0 {
+            // string is null terminated
+            return l;
+        }
+        // ASCII to base64 conversion:
+        let mut bits: c_long = if c < 58 {
+            (c - 46) as c_long // ./0123456789
+        } else if c < 91 {
+            (c - 53) as c_long // A-Z
+        } else {
+            (c - 59) as c_long // a-z
+        };
+        bits <<= 6 * x;
+        l |= bits;
+    }
+    return l;
 }
 
 #[no_mangle]
diff --git a/tests/.gitignore b/tests/.gitignore
index c5a743e74f6964efc7476545fcce4229e2653fc7..d0bc0d66b343fcc3e240bfbcf4eb4d1a286f25a5 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -29,6 +29,7 @@
 /setid
 /sprintf
 /stdlib/strtol
+/stdlib/a64l
 /string/strncmp
 /string/strcspn
 /string/strchr
diff --git a/tests/Makefile b/tests/Makefile
index ea41ffa7a2a7761ab75e4e116579d9ef4276f051..8a626402c063dec9558d912e76b33b1d0906d024 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -24,6 +24,7 @@ BINS=\
 	sleep \
 	sprintf \
 	stdlib/strtol \
+	stdlib/a64l \
 	string/strncmp \
 	string/strcspn \
 	string/strchr \
diff --git a/tests/stdlib/a64l.c b/tests/stdlib/a64l.c
new file mode 100644
index 0000000000000000000000000000000000000000..8036d9e3fb0c85391effadde4986a17fc66d8bbc
--- /dev/null
+++ b/tests/stdlib/a64l.c
@@ -0,0 +1,22 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(int argc, char* argv[]) {
+    char * s = "azAZ9."; // test boundaries
+    long l = a64l(s);
+    if (l != 194301926) {
+        printf("Invalid result: a64l(%s) = %ld\n", s, l);
+        return 1;
+    }
+    printf("Correct a64l: %s = %ld\n", s, l);
+
+    
+    s = "azA"; // test null terminated string
+    l = a64l(s);
+    if (l != 53222) {
+        printf("Invalid result: a64l(%s) = %ld\n", s, l);
+        return 1;
+    }
+    printf("Correct a64l: %s = %ld\n", s, l);
+    return 0;
+}