diff --git a/src/arith_uint256.h b/src/arith_uint256.h
--- a/src/arith_uint256.h
+++ b/src/arith_uint256.h
@@ -9,6 +9,7 @@
 #include <cassert>
 #include <cstdint>
 #include <cstring>
+#include <limits>
 #include <stdexcept>
 #include <string>
 #include <vector>
@@ -28,11 +29,19 @@
 
 public:
     base_uint() {
+        static_assert(
+            BITS / 32 > 0 && BITS % 32 == 0,
+            "Template parameter BITS must be a positive multiple of 32.");
+
         for (int i = 0; i < WIDTH; i++)
             pn[i] = 0;
     }
 
     base_uint(const base_uint &b) {
+        static_assert(
+            BITS / 32 > 0 && BITS % 32 == 0,
+            "Template parameter BITS must be a positive multiple of 32.");
+
         for (int i = 0; i < WIDTH; i++)
             pn[i] = b.pn[i];
     }
@@ -44,6 +53,10 @@
     }
 
     base_uint(uint64_t b) {
+        static_assert(
+            BITS / 32 > 0 && BITS % 32 == 0,
+            "Template parameter BITS must be a positive multiple of 32.");
+
         pn[0] = (unsigned int)b;
         pn[1] = (unsigned int)(b >> 32);
         for (int i = 2; i < WIDTH; i++)
@@ -146,7 +159,7 @@
     base_uint &operator++() {
         // prefix operator
         int i = 0;
-        while (++pn[i] == 0 && i < WIDTH - 1)
+        while (i < WIDTH && ++pn[i] == 0)
             i++;
         return *this;
     }
@@ -161,7 +174,7 @@
     base_uint &operator--() {
         // prefix operator
         int i = 0;
-        while (--pn[i] == (uint32_t)-1 && i < WIDTH - 1)
+        while (i < WIDTH && --pn[i] == std::numeric_limits<uint32_t>::max())
             i++;
         return *this;
     }
diff --git a/src/arith_uint256.cpp b/src/arith_uint256.cpp
--- a/src/arith_uint256.cpp
+++ b/src/arith_uint256.cpp
@@ -14,6 +14,9 @@
 
 template <unsigned int BITS>
 base_uint<BITS>::base_uint(const std::string &str) {
+    static_assert(BITS / 32 > 0 && BITS % 32 == 0,
+                  "Template parameter BITS must be a positive multiple of 32.");
+
     SetHex(str);
 }