diff --git a/src/commands.cc b/src/commands.cc
index 54e1a40e..6feb1b2c 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -1143,7 +1143,7 @@ const CommandDesc debug_cmd = {
         [](const Context& context, CompletionFlags flags,
            const String& prefix, ByteCount cursor_pos) -> Completions {
                auto c = {"info", "buffers", "options", "memory", "shared-strings",
-                         "profile-hash-maps", "faces", "mappings"};
+                         "profile-hash-maps", "faces", "mappings", "regex"};
                return { 0_byte, cursor_pos, complete(prefix, cursor_pos, c) };
     }),
     [](const ParametersParser& parser, Context& context, const ShellContext&)
@@ -1216,6 +1216,14 @@ const CommandDesc debug_cmd = {
                                           keymaps.get_mapping(key, m).docstring));
             }
         }
+        else if (parser[0] == "regex")
+        {
+            if (parser.positional_count() != 2)
+                throw runtime_error("expected a regex");
+
+            write_to_debug_buffer(format(" * {}:\n{}",
+                                  parser[1], dump_regex(compile_regex(parser[1], RegexCompileFlags::None))));
+        }
         else
             throw runtime_error(format("no such debug command: '{}'", parser[0]));
     }
diff --git a/src/regex_impl.cc b/src/regex_impl.cc
index 0202cb85..46ccbae0 100644
--- a/src/regex_impl.cc
+++ b/src/regex_impl.cc
@@ -992,60 +992,63 @@ private:
     ParsedRegex& m_parsed_regex;
 };
 
-void dump_regex(const CompiledRegex& program)
+String dump_regex(const CompiledRegex& program)
 {
+    String res;
     int count = 0;
     for (auto& inst : program.instructions)
     {
-        printf(" %03d     ", count++);
+        char buf[10];
+        sprintf(buf, " %03d     ", count++);
+        res += buf;
         switch (inst.op)
         {
             case CompiledRegex::Literal:
-                printf("literal %lc\n", inst.param);
+                res += format("literal {}\n", inst.param);
                 break;
             case CompiledRegex::Literal_IgnoreCase:
-                printf("literal (ignore case) %lc\n", inst.param);
+                res += format("literal (ignore case) {}\n", inst.param);
                 break;
             case CompiledRegex::AnyChar:
-                printf("any char\n");
+                res += "any char\n";
                 break;
             case CompiledRegex::Jump:
-                printf("jump %u\n", inst.param);
+                res += format("jump {}\n", inst.param);
                 break;
             case CompiledRegex::Split_PrioritizeParent:
             case CompiledRegex::Split_PrioritizeChild:
             {
-                printf("split (prioritize %s) %u\n",
-                       inst.op == CompiledRegex::Split_PrioritizeParent ? "parent" : "child",
-                       inst.param);
+                res += format("split (prioritize {}) {}\n",
+                              inst.op == CompiledRegex::Split_PrioritizeParent ? "parent" : "child",
+                              inst.param);
                 break;
             }
             case CompiledRegex::Save:
-                printf("save %d\n", inst.param);
+                res += format("save {}\n", inst.param);
                 break;
             case CompiledRegex::Class:
-                printf("class %d\n", inst.param);
+                res += format("class {}\n", inst.param);
                 break;
             case CompiledRegex::CharacterType:
-                printf("character type %d\n", inst.param);
+                res += format("character type {}\n", inst.param);
                 break;
             case CompiledRegex::LineStart:
-                printf("line start\n");
+                res += "line start\n";
                 break;
             case CompiledRegex::LineEnd:
-                printf("line end\n");
+                res += "line end\n";
                 break;
             case CompiledRegex::WordBoundary:
-                printf("word boundary\n");
+                res += "word boundary\n";
                 break;
             case CompiledRegex::NotWordBoundary:
-                printf("not word boundary\n");
+                res += "not word boundary\n";
                 break;
             case CompiledRegex::SubjectBegin:
-                printf("subject begin\n");
+                res += "subject begin\n";
                 break;
             case CompiledRegex::SubjectEnd:
-                printf("subject end\n");
+                res += "subject end\n";
                 break;
             case CompiledRegex::LookAhead:
             case CompiledRegex::NegativeLookAhead:
@@ -1078,16 +1081,17 @@ void dump_regex(const CompiledRegex& program)
                 String str;
                 for (auto it = program.lookarounds.begin() + inst.param; *it != -1; ++it)
                     utf8::dump(std::back_inserter(str), *it);
-                printf("%s (%s)\n", name, str.c_str());
+                res += format("{} ({})\n", name, str);
                 break;
             }
             case CompiledRegex::FindNextStart:
-                printf("find next start\n");
+                res += "find next start\n";
                 break;
             case CompiledRegex::Match:
-                printf("match\n");
+                res += "match\n";
         }
     }
+    return res;
 }
 
 CompiledRegex compile_regex(StringView re, RegexCompileFlags flags)
@@ -1134,7 +1138,7 @@ struct TestVM : CompiledRegex, ThreadedRegexVM<const char*, dir>
         : CompiledRegex{compile_regex(re, dir == MatchDirection::Forward ?
                                           RegexCompileFlags::None : RegexCompileFlags::Backward)},
           VMType{(const CompiledRegex&)*this}
-    { if (dump) dump_regex(*this); }
+    { if (dump) printf(dump_regex(*this).c_str()); }
 
     bool exec(StringView re, RegexExecFlags flags = RegexExecFlags::AnyMatch)
     {
diff --git a/src/regex_impl.hh b/src/regex_impl.hh
index 99160f96..5f522b60 100644
--- a/src/regex_impl.hh
+++ b/src/regex_impl.hh
@@ -112,6 +112,8 @@ struct CompiledRegex : RefCountable, UseMemoryDomain<MemoryDomain::Regex>
     std::unique_ptr<StartDesc> backward_start_desc;
 };
 
+String dump_regex(const CompiledRegex& program);
+
 enum class RegexCompileFlags
 {
     None     = 0,
diff --git a/src/string_utils.cc b/src/string_utils.cc
index 801cd5a3..a0f74dc6 100644
--- a/src/string_utils.cc
+++ b/src/string_utils.cc
@@ -125,6 +125,13 @@ InplaceString<15> to_string(int val)
     return res;
 }
 
+InplaceString<15> to_string(unsigned val)
+{
+    InplaceString<15> res;
+    res.m_length = sprintf(res.m_data, "%u", val);
+    return res;
+}
+
 InplaceString<23> to_string(long int val)
 {
     InplaceString<23> res;
diff --git a/src/string_utils.hh b/src/string_utils.hh
index e8442fc2..1db9da24 100644
--- a/src/string_utils.hh
+++ b/src/string_utils.hh
@@ -72,6 +72,7 @@ struct Hex { size_t val; };
 constexpr Hex hex(size_t val) { return {val}; }
 
 InplaceString<15> to_string(int val);
+InplaceString<15> to_string(unsigned val);
 InplaceString<23> to_string(long int val);
 InplaceString<23> to_string(size_t val);
 InplaceString<23> to_string(long long int val);