diff --git a/include/pocketpy/str.h b/include/pocketpy/str.h
index e303c91f..7debedba 100644
--- a/include/pocketpy/str.h
+++ b/include/pocketpy/str.h
@@ -148,7 +148,7 @@ struct SStream{
     SStream& operator<<(char);
     SStream& operator<<(StrName);
 
-    void write_hex(unsigned char);
+    void write_hex(unsigned char, bool non_zero=false);
     void write_hex(void*);
     void write_hex(i64);
 };
diff --git a/src/str.cpp b/src/str.cpp
index b252b258..cdbb8e45 100644
--- a/src/str.cpp
+++ b/src/str.cpp
@@ -521,33 +521,48 @@ int utf8len(unsigned char c, bool suppress){
         return *this;
     }
 
-    void SStream::write_hex(unsigned char c){
-        *this << "0123456789ABCDEF"[c >> 4];
-        *this << "0123456789ABCDEF"[c & 0xf];
+    void SStream::write_hex(unsigned char c, bool non_zero){
+        unsigned char high = c >> 4;
+        unsigned char low = c & 0xf;
+        if(non_zero){
+            if(high) (*this) << "0123456789abcdef"[high];
+            if(high || low) (*this) << "0123456789abcdef"[low];
+        }else{
+            (*this) << "0123456789abcdef"[high];
+            (*this) << "0123456789abcdef"[low];
+        }
     }
 
     void SStream::write_hex(void* p){
+        if(p == nullptr){
+            (*this) << "0x0";
+            return;
+        }
         (*this) << "0x";
         uintptr_t p_t = reinterpret_cast<uintptr_t>(p);
+        bool non_zero = true;
         for(int i=sizeof(void*)-1; i>=0; i--){
             unsigned char cpnt = (p_t >> (i * 8)) & 0xff;
-            write_hex(cpnt);
+            write_hex(cpnt, non_zero);
+            if(cpnt != 0) non_zero = false;
         }
     }
 
     void SStream::write_hex(i64 val){
+        if(val == 0){
+            (*this) << "0x0";
+            return;
+        }
         if(val < 0){
             (*this) << "-";
             val = -val;
         }
         (*this) << "0x";
-        if(val == 0){
-            (*this) << "0";
-            return;
-        }
+        bool non_zero = true;
         for(int i=56; i>=0; i-=8){
             unsigned char cpnt = (val >> i) & 0xff;
-            if(cpnt != 0) write_hex(cpnt);
+            write_hex(cpnt, non_zero);
+            if(cpnt != 0) non_zero = false;
         }
     }
 
diff --git a/tests/04_str.py b/tests/04_str.py
index bc820c50..79cc89cb 100644
--- a/tests/04_str.py
+++ b/tests/04_str.py
@@ -183,5 +183,25 @@ stack=[1,2,3,4]; assert f"{stack[2:]}" == '[3, 4]'
 
 assert repr('\x1f\x1e\x1f') == '\'\\x1f\\x1e\\x1f\''
 
-assert hex(255) == '0xFF'
-assert hex(-42) == '-0x2A'
+
+assert hex(-42) == '-0x2a'
+assert hex(42) == '0x2a'
+
+assert hex(0) == '0x0'
+assert hex(1) == '0x1'
+assert hex(15) == '0xf'
+assert hex(16) == '0x10'
+assert hex(255) == '0xff'
+assert hex(256) == '0x100'
+assert hex(257) == '0x101'
+assert hex(17) == '0x11'
+
+import c
+assert repr(c.NULL) == '<void* at 0x0>'
+assert repr(c.void_p(1)) == '<void* at 0x1>'
+assert repr(c.void_p(15)) == '<void* at 0xf>'
+assert repr(c.void_p(16)) == '<void* at 0x10>'
+assert repr(c.void_p(255)) == '<void* at 0xff>'
+assert repr(c.void_p(256)) == '<void* at 0x100>'
+assert repr(c.void_p(257)) == '<void* at 0x101>'
+assert repr(c.void_p(17)) == '<void* at 0x11>'