diff --git a/Recipe b/Recipe
index 894ab2a9..2ce432c1 100644
--- a/Recipe
+++ b/Recipe
@@ -389,8 +389,10 @@ osxlaunch : [UT] osxlaunch
 
 fuzzterm : [UT] UXTERM CHARSET MISC version uxmisc uxucs fuzzterm time settings
 	 + uxstore be_none uxnogtk memory
-testcrypt : [UT] testcrypt SSHCRYPTO marshal utils memory tree234 uxutils
-testcrypt : [C] testcrypt SSHCRYPTO marshal utils memory tree234 winmiscs
+testcrypt : [UT] testcrypt SSHCRYPTO sshprime marshal utils memory tree234
+          + uxutils
+testcrypt : [C] testcrypt SSHCRYPTO sshprime marshal utils memory tree234
+          + winmiscs
 testzlib : [UT] testzlib sshzlib memory
 
 uppity   : [UT] uxserver SSHSERVER UXMISC uxsignal uxnoise uxgss uxnogtk
diff --git a/testcrypt.c b/testcrypt.c
index 05615c93..da228985 100644
--- a/testcrypt.c
+++ b/testcrypt.c
@@ -900,6 +900,16 @@ bool crcda_detect(ptrlen packet, ptrlen iv)
 
 #define return_void(out, expression) (expression)
 
+static void no_progress(void *param, int action, int phase, int iprogress) {}
+
+mp_int *primegen_wrapper(
+    int bits, int modulus, int residue, mp_int *factor, unsigned firstbits)
+{
+    return primegen(bits, modulus, residue, factor,
+                    0, no_progress, NULL, firstbits);
+}
+#define primegen primegen_wrapper
+
 #define VALTYPE_TYPEDEF(n,t,f)                  \
     typedef t TD_val_##n;                       \
     typedef t *TD_out_val_##n;
@@ -967,8 +977,19 @@ typedef RsaSsh1Order TD_rsaorder;
         return_##rettype(out, function(arg1, arg2, arg3, arg4));        \
     }
 
+#define FUNC5(rettype, function, type1, type2, type3, type4, type5)     \
+    static void handle_##function(BinarySource *in, strbuf *out) {      \
+        TD_##type1 arg1 = get_##type1(in);                              \
+        TD_##type2 arg2 = get_##type2(in);                              \
+        TD_##type3 arg3 = get_##type3(in);                              \
+        TD_##type4 arg4 = get_##type4(in);                              \
+        TD_##type5 arg5 = get_##type5(in);                              \
+        return_##rettype(out, function(arg1, arg2, arg3, arg4, arg5));  \
+    }
+
 #include "testcrypt.h"
 
+#undef FUNC5
 #undef FUNC4
 #undef FUNC3
 #undef FUNC2
@@ -1002,9 +1023,11 @@ static void process_line(BinarySource *in, strbuf *out)
 #define FUNC2 FUNC
 #define FUNC3 FUNC
 #define FUNC4 FUNC
+#define FUNC5 FUNC
 
 #include "testcrypt.h"
 
+#undef FUNC5
 #undef FUNC4
 #undef FUNC3
 #undef FUNC2
diff --git a/testcrypt.h b/testcrypt.h
index ae99b51b..bc7c6772 100644
--- a/testcrypt.h
+++ b/testcrypt.h
@@ -238,6 +238,7 @@ FUNC1(uint, crc32_rfc1662, val_string_ptrlen)
 FUNC1(uint, crc32_ssh1, val_string_ptrlen)
 FUNC2(uint, crc32_update, uint, val_string_ptrlen)
 FUNC2(boolean, crcda_detect, val_string_ptrlen, val_string_ptrlen)
+FUNC5(val_mpint, primegen, uint, uint, uint, val_mpint, uint)
 
 /*
  * These functions aren't part of PuTTY's own API, but are additions