diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
index 4ac169e..9cb4482 100644
--- a/crypto/dh/dh_check.c
+++ b/crypto/dh/dh_check.c
@@ -184,6 +184,20 @@ int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
     BN_CTX *ctx = NULL;
 
     *ret = 0;
+    
+    /* Don't do any checks at all with an excessively large modulus */
+    if (BN_num_bits(dh->p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
+        DHerr(DH_F_DH_CHECK_EX, DH_R_MODULUS_TOO_LARGE);
+        *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID;
+        return 0;
+    }
+
+    if (dh->q != NULL && BN_ucmp(dh->p, dh->q) < 0) {
+        *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID;
+        return 1;
+    }
+
+
     ctx = BN_CTX_new();
     if (ctx == NULL)
         goto err;
diff --git a/crypto/dh/dh_err.c b/crypto/dh/dh_err.c
index 7285587..85f1e51 100644
--- a/crypto/dh/dh_err.c
+++ b/crypto/dh/dh_err.c
@@ -81,6 +81,7 @@ static const ERR_STRING_DATA DH_str_reasons[] = {
     {ERR_PACK(ERR_LIB_DH, 0, DH_R_PARAMETER_ENCODING_ERROR),
     "parameter encoding error"},
     {ERR_PACK(ERR_LIB_DH, 0, DH_R_PEER_KEY_ERROR), "peer key error"},
+    {ERR_PACK(ERR_LIB_DH, 0, DH_R_Q_TOO_LARGE), "q too large"},
     {ERR_PACK(ERR_LIB_DH, 0, DH_R_SHARED_INFO_ERROR), "shared info error"},
     {ERR_PACK(ERR_LIB_DH, 0, DH_R_UNABLE_TO_CHECK_GENERATOR),
     "unable to check generator"},
diff --git a/crypto/dh/dh_key.c b/crypto/dh/dh_key.c
index 117f2fa..b4c789d 100644
--- a/crypto/dh/dh_key.c
+++ b/crypto/dh/dh_key.c
@@ -109,6 +109,12 @@ static int generate_key(DH *dh)
     BN_MONT_CTX *mont = NULL;
     BIGNUM *pub_key = NULL, *priv_key = NULL;
 
+    if (dh->q != NULL
+        && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) {
+        DHerr(DH_F_GENERATE_KEY, DH_R_Q_TOO_LARGE);
+        return 0;
+    }
+
     if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
         DHerr(DH_F_GENERATE_KEY, DH_R_MODULUS_TOO_LARGE);
         return 0;
@@ -202,6 +208,12 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
     int ret = -1;
     int check_result;
 
+    if (dh->q != NULL
+        && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) {
+        DHerr(DH_F_COMPUTE_KEY, DH_R_Q_TOO_LARGE);
+        goto err;
+    }
+
     if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
         DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
         goto err;
diff --git a/crypto/err/openssl.txt b/crypto/err/openssl.txt
index 7e17763..405c116 100644
--- a/crypto/err/openssl.txt
+++ b/crypto/err/openssl.txt
@@ -2100,6 +2100,7 @@ DH_R_NO_PARAMETERS_SET:107:no parameters set
 DH_R_NO_PRIVATE_VALUE:100:no private value
 DH_R_PARAMETER_ENCODING_ERROR:105:parameter encoding error
 DH_R_PEER_KEY_ERROR:111:peer key error
+DH_R_Q_TOO_LARGE:130:q too large
 DH_R_SHARED_INFO_ERROR:113:shared info error
 DH_R_UNABLE_TO_CHECK_GENERATOR:121:unable to check generator
 DSA_R_BAD_Q_VALUE:102:bad q value
diff --git a/include/openssl/dh.h b/include/openssl/dh.h
index 3527540..a50ad96 100644
--- a/include/openssl/dh.h
+++ b/include/openssl/dh.h
@@ -68,14 +68,15 @@ DECLARE_ASN1_ITEM(DHparams)
 /* #define DH_GENERATOR_3       3 */
 # define DH_GENERATOR_5          5
 
-/* DH_check error codes */
+/* DH_check error codes, some of them shared with DH_check_pub_key */
 # define DH_CHECK_P_NOT_PRIME            0x01
 # define DH_CHECK_P_NOT_SAFE_PRIME       0x02
 # define DH_UNABLE_TO_CHECK_GENERATOR    0x04
 # define DH_NOT_SUITABLE_GENERATOR       0x08
 # define DH_CHECK_Q_NOT_PRIME            0x10
-# define DH_CHECK_INVALID_Q_VALUE        0x20
+# define DH_CHECK_INVALID_Q_VALUE        0x20  /* +DH_check_pub_key */
 # define DH_CHECK_INVALID_J_VALUE        0x40
+# define DH_MODULUS_TOO_LARGE            0x100
 
 /* DH_check_pub_key error codes */
 # define DH_CHECK_PUBKEY_TOO_SMALL       0x01
diff --git a/include/openssl/dherr.h b/include/openssl/dherr.h
index 916b3be..88c3a6c 100644
--- a/include/openssl/dherr.h
+++ b/include/openssl/dherr.h
@@ -81,6 +81,7 @@ int ERR_load_DH_strings(void);
 #  define DH_R_NO_PRIVATE_VALUE                            100
 #  define DH_R_PARAMETER_ENCODING_ERROR                    105
 #  define DH_R_PEER_KEY_ERROR                              111
+#  define DH_R_Q_TOO_LARGE                                 130
 #  define DH_R_SHARED_INFO_ERROR                           113
 #  define DH_R_UNABLE_TO_CHECK_GENERATOR                   121