diff --git a/Userland/Libraries/LibRegex/RegexDebug.h b/Userland/Libraries/LibRegex/RegexDebug.h
index eb45ba55bf..7ac77d38a8 100644
--- a/Userland/Libraries/LibRegex/RegexDebug.h
+++ b/Userland/Libraries/LibRegex/RegexDebug.h
@@ -81,11 +81,11 @@ public:
         builder.append(execution_result_name(result));
         builder.appendff(", fc: {}, ss: {}", input.fail_counter, input.saved_positions.size());
         if (result == ExecutionResult::Succeeded) {
-            builder.appendf(", ip: %lu/%lu, sp: %lu/%lu", state.instruction_position, bytecode.size() - 1, state.string_position, input.view.length() - 1);
+            builder.appendff(", ip: {}/{}, sp: {}/{}", state.instruction_position, bytecode.size() - 1, state.string_position, input.view.length() - 1);
         } else if (result == ExecutionResult::Fork_PrioHigh) {
-            builder.appendf(", next ip: %lu", state.fork_at_position + opcode.size());
+            builder.appendff(", next ip: {}", state.fork_at_position + opcode.size());
         } else if (result != ExecutionResult::Failed) {
-            builder.appendf(", next ip: %lu", state.instruction_position + opcode.size());
+            builder.appendff(", next ip: {}", state.instruction_position + opcode.size());
         }
 
         fprintf(m_file, " | %-20s\n", builder.to_string().characters());
@@ -102,7 +102,7 @@ public:
     void print_header()
     {
         StringBuilder builder;
-        builder.appendf("%-15s | %-5s | %-9s | %-35s | %-30s | %-20s | %-20s\n", "System", "Index", "Recursion", "OpCode", "Arguments", "State", "Result");
+        builder.appendff("{:15} | {:5} | {:9} | {:35} | {:30} | {:20} | {:20}\n", "System", "Index", "Recursion", "OpCode", "Arguments", "State", "Result");
         auto length = builder.length();
         for (size_t i = 0; i < length; ++i) {
             builder.append('=');
diff --git a/Userland/Libraries/LibRegex/RegexMatcher.cpp b/Userland/Libraries/LibRegex/RegexMatcher.cpp
index 568267bf16..e416ebe6e4 100644
--- a/Userland/Libraries/LibRegex/RegexMatcher.cpp
+++ b/Userland/Libraries/LibRegex/RegexMatcher.cpp
@@ -44,12 +44,12 @@ template<class Parser>
 String Regex<Parser>::error_string(Optional<String> message) const
 {
     StringBuilder eb;
-    eb.appendf("Error during parsing of regular expression:\n");
-    eb.appendf("    %s\n    ", pattern_value.characters());
+    eb.append("Error during parsing of regular expression:\n");
+    eb.appendff("    {}\n    ", pattern_value);
     for (size_t i = 0; i < parser_result.error_token.position(); ++i)
-        eb.append(" ");
+        eb.append(' ');
 
-    eb.appendf("^---- %s", message.value_or(get_error_string(parser_result.error)).characters());
+    eb.appendff("^---- {}", message.value_or(get_error_string(parser_result.error)));
     return eb.build();
 }