diff --git a/src/Anon.cc b/src/Anon.cc
index facc5dbbb2..fbcbc00a1a 100644
--- a/src/Anon.cc
+++ b/src/Anon.cc
@@ -259,6 +259,10 @@ AnonymizeIPAddr_A50::Node* AnonymizeIPAddr_A50::make_peer(ipaddr32_t a, Node* n)
     // swivel is first bit 'a' and 'old->input' differ.
     int swivel = bi_ffs(a ^ n->input);
 
+    // Shifting by more than 31 bits below results in undefined behavior.
+    // This shouldn't be possible, but check anyways.
+    ASSERT(swivel > 0);
+
     // bitvalue is the value of that bit of 'a'.
     int bitvalue = (a >> (32 - swivel)) & 1;
 
@@ -305,6 +309,10 @@ AnonymizeIPAddr_A50::Node* AnonymizeIPAddr_A50::find_node(ipaddr32_t a) {
             // differ.
             int swivel = bi_ffs(n->child[0]->input ^ n->child[1]->input);
 
+            // Shifting by more than 31 bits below results in undefined behavior.
+            // This shouldn't be possible, but check anyways.
+            ASSERT(swivel > 0);
+
             if ( bi_ffs(a ^ n->input) < swivel )
                 // Input differs earlier.
                 n = make_peer(a, n);
diff --git a/src/Val.cc b/src/Val.cc
index 35b088870c..fe87c42aa0 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -751,7 +751,7 @@ IPAddr SubNetVal::Mask() const {
     for ( w = subnet_val->Length(); w >= 32; w -= 32 )
         *(mp++) = 0xffffffff;
 
-    *mp = ~((1 << (32 - w)) - 1);
+    *mp = ~((static_cast<uint32_t>(1) << (32 - w)) - 1);
 
     while ( ++mp < m + 4 )
         *mp = 0;