diff --git a/crypto/dh/dh_lib.c b/crypto/dh/dh_lib.c
index e8a66878ab39c..46aba02bad75d 100644
--- a/crypto/dh/dh_lib.c
+++ b/crypto/dh/dh_lib.c
@@ -187,12 +187,16 @@ void *DH_get_ex_data(const DH *d, int idx)
 
 int DH_bits(const DH *dh)
 {
-    return BN_num_bits(dh->params.p);
+    if (dh->params.p != NULL)
+        return BN_num_bits(dh->params.p);
+    return -1;
 }
 
 int DH_size(const DH *dh)
 {
-    return BN_num_bytes(dh->params.p);
+    if (dh->params.p != NULL)
+        return BN_num_bytes(dh->params.p);
+    return -1;
 }
 
 int DH_security_bits(const DH *dh)
@@ -204,7 +208,9 @@ int DH_security_bits(const DH *dh)
         N = dh->length;
     else
         N = -1;
-    return BN_security_bits(BN_num_bits(dh->params.p), N);
+    if (dh->params.p != NULL)
+        return BN_security_bits(BN_num_bits(dh->params.p), N);
+    return -1;
 }
 
 void DH_get0_pqg(const DH *dh,
diff --git a/doc/man3/DH_size.pod b/doc/man3/DH_size.pod
index 099c1bad3f8e4..99e34034f2cbb 100644
--- a/doc/man3/DH_size.pod
+++ b/doc/man3/DH_size.pod
@@ -38,11 +38,14 @@ key. See L<BN_security_bits(3)>.
 
 =head1 RETURN VALUES
 
-DH_bits() returns the number of bits in the key.
+DH_bits() returns the number of bits in the key, or -1 if
+B<dh> doesn't hold any key parameters.
 
-DH_size() returns the prime size of Diffie-Hellman in bytes.
+DH_size() returns the prime size of Diffie-Hellman in bytes, or -1 if
+B<dh> doesn't hold any key parameters.
 
-DH_security_bits() returns the number of security bits.
+DH_security_bits() returns the number of security bits, or -1 if
+B<dh> doesn't hold any key parameters.
 
 =head1 SEE ALSO