diff --git a/ctl/string.h b/ctl/string.h
index a3488cd7a25..b2941588d1a 100644
--- a/ctl/string.h
+++ b/ctl/string.h
@@ -426,31 +426,31 @@ static_assert(sizeof(__::small_string) == __::string_size);
 static_assert(sizeof(__::big_string) == __::string_size);
 
 ctl::string
-to_string(int);
+to_string(int) noexcept;
 
 ctl::string
-to_string(long);
+to_string(long) noexcept;
 
 ctl::string
-to_string(long long);
+to_string(long long) noexcept;
 
 ctl::string
-to_string(unsigned);
+to_string(unsigned) noexcept;
 
 ctl::string
-to_string(unsigned long);
+to_string(unsigned long) noexcept;
 
 ctl::string
-to_string(unsigned long long);
+to_string(unsigned long long) noexcept;
 
 ctl::string
-to_string(float);
+to_string(float) noexcept;
 
 ctl::string
-to_string(double);
+to_string(double) noexcept;
 
 ctl::string
-to_string(long double);
+to_string(long double) noexcept;
 
 } // namespace ctl
 
diff --git a/ctl/to_string.cc b/ctl/to_string.cc
index fb54968e918..a66bb703149 100644
--- a/ctl/to_string.cc
+++ b/ctl/to_string.cc
@@ -27,49 +27,49 @@ namespace ctl {
 extern const double_conversion::DoubleToStringConverter kDoubleToPrintfG;
 
 string
-to_string(int value)
+to_string(int value) noexcept
 {
     char buf[12];
     return { buf, FormatInt32(buf, value) - buf };
 }
 
 string
-to_string(unsigned value)
+to_string(unsigned value) noexcept
 {
     char buf[12];
     return { buf, FormatUint32(buf, value) - buf };
 }
 
 string
-to_string(long value)
+to_string(long value) noexcept
 {
     char buf[21];
     return { buf, FormatInt64(buf, value) - buf };
 }
 
 string
-to_string(unsigned long value)
+to_string(unsigned long value) noexcept
 {
     char buf[21];
     return { buf, FormatUint64(buf, value) - buf };
 }
 
 string
-to_string(long long value)
+to_string(long long value) noexcept
 {
     char buf[21];
     return { buf, FormatInt64(buf, value) - buf };
 }
 
 string
-to_string(unsigned long long value)
+to_string(unsigned long long value) noexcept
 {
     char buf[21];
     return { buf, FormatUint64(buf, value) - buf };
 }
 
 string
-to_string(float value)
+to_string(float value) noexcept
 {
     char buf[128];
     double_conversion::StringBuilder b(buf, sizeof(buf));
@@ -79,7 +79,7 @@ to_string(float value)
 }
 
 string
-to_string(double value)
+to_string(double value) noexcept
 {
     char buf[128];
     double_conversion::StringBuilder b(buf, sizeof(buf));
@@ -89,7 +89,7 @@ to_string(double value)
 }
 
 string
-to_string(long double value)
+to_string(long double value) noexcept
 {
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
     return to_string((double)value);
diff --git a/test/ctl/to_string_test.cc b/test/ctl/to_string_test.cc
index 8cba51e6003..69841c7ad59 100644
--- a/test/ctl/to_string_test.cc
+++ b/test/ctl/to_string_test.cc
@@ -17,7 +17,6 @@
 // PERFORMANCE OF THIS SOFTWARE.
 
 #include "ctl/string.h"
-#include "libc/intrin/kprintf.h"
 #include "libc/limits.h"
 #include "libc/math.h"
 #include "libc/mem/leaks.h"