diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index d7e3a2cdb0b..c1dadeee087 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -28,13 +28,13 @@
 #include <algorithm>
 #include <chrono>
 #include <iostream>
+#include <sstream>
 #include <cstring>
 #include <optional>
 #include <unistd.h>
 #include <sys/time.h>
 #include <fstream>
 #include <functional>
-#include <iostream>
 
 #include <nlohmann/json.hpp>
 #include <boost/container/small_vector.hpp>
diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index ee2b6b80790..8c0f9d1f2f7 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -20,8 +20,6 @@
 #pragma clang diagnostic ignored "-Wunneeded-internal-declaration"
 #endif
 
-#include <boost/lexical_cast.hpp>
-
 #include "nixexpr.hh"
 #include "parser-tab.hh"
 
@@ -129,9 +127,10 @@ or          { return OR_KW; }
 
 {ID}        { yylval->id = {yytext, (size_t) yyleng}; return ID; }
 {INT}       { errno = 0;
-              try {
-                  yylval->n = boost::lexical_cast<int64_t>(yytext);
-              } catch (const boost::bad_lexical_cast &) {
+              std::optional<int64_t> numMay = string2Int<int64_t>(yytext);
+              if (numMay.has_value()) {
+                  yylval->n = *numMay;
+              } else {
                   throw ParseError(ErrorInfo{
                       .msg = HintFmt("invalid integer '%1%'", yytext),
                       .pos = state->positions[CUR_POS],
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index c1e2b044882..44198a25238 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -6,6 +6,7 @@
 #include "print.hh"
 
 #include <cstdlib>
+#include <sstream>
 
 namespace nix {
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 1b1a9be3d02..7371bd488f0 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -26,6 +26,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <sstream>
 #include <regex>
 
 #ifndef _WIN32
diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index d53fadac75a..920490cfad4 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -1,5 +1,6 @@
 #include <limits>
 #include <unordered_set>
+#include <sstream>
 
 #include "print.hh"
 #include "ansicolor.hh"
diff --git a/src/libmain/progress-bar.cc b/src/libmain/progress-bar.cc
index ce45eae2ba1..bb4c52ef7ea 100644
--- a/src/libmain/progress-bar.cc
+++ b/src/libmain/progress-bar.cc
@@ -7,6 +7,7 @@
 #include <atomic>
 #include <map>
 #include <thread>
+#include <sstream>
 #include <iostream>
 #include <chrono>
 
diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index 5153ca64fb1..56e47697c96 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -18,6 +18,7 @@
 #include <future>
 #include <regex>
 #include <fstream>
+#include <sstream>
 
 #include <nlohmann/json.hpp>
 
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index eb6a4e69039..4e231ca99eb 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -19,6 +19,8 @@
 # include "monitor-fd.hh"
 #endif
 
+#include <sstream>
+
 namespace nix::daemon {
 
 Sink & operator << (Sink & sink, const Logger::Fields & fields)
diff --git a/src/libstore/machines.cc b/src/libstore/machines.cc
index 20f24e8833b..256cf918892 100644
--- a/src/libstore/machines.cc
+++ b/src/libstore/machines.cc
@@ -148,7 +148,7 @@ static Machine parseBuilderLine(const std::set<std::string> & defaultSystems, co
     };
 
     auto parseFloatField = [&](size_t fieldIndex) {
-        const auto result = string2Int<float>(tokens[fieldIndex]);
+        const auto result = string2Float<float>(tokens[fieldIndex]);
         if (!result) {
             throw FormatError("bad machine specification: failed to convert column #%lu in a row: '%s' to 'float'", fieldIndex, line);
         }
diff --git a/src/libutil/current-process.cc b/src/libutil/current-process.cc
index 9efb68d47a2..6ca48220d21 100644
--- a/src/libutil/current-process.cc
+++ b/src/libutil/current-process.cc
@@ -7,6 +7,7 @@
 #include "file-system.hh"
 #include "processes.hh"
 #include "signals.hh"
+#include <math.h>
 
 #ifdef __APPLE__
 # include <mach-o/dyld.h>
diff --git a/src/libutil/file-system.hh b/src/libutil/file-system.hh
index 933e88441e7..c6b6ecedbb7 100644
--- a/src/libutil/file-system.hh
+++ b/src/libutil/file-system.hh
@@ -20,8 +20,6 @@
 #endif
 #include <signal.h>
 
-#include <boost/lexical_cast.hpp>
-
 #include <atomic>
 #include <functional>
 #include <map>
diff --git a/src/libutil/logging.cc b/src/libutil/logging.cc
index 2511c88499f..5fa01f0d969 100644
--- a/src/libutil/logging.cc
+++ b/src/libutil/logging.cc
@@ -8,6 +8,7 @@
 #include "position.hh"
 
 #include <atomic>
+#include <sstream>
 #include <nlohmann/json.hpp>
 #include <iostream>
 
diff --git a/src/libutil/processes.hh b/src/libutil/processes.hh
index 9d5367b024c..168fcaa5559 100644
--- a/src/libutil/processes.hh
+++ b/src/libutil/processes.hh
@@ -12,8 +12,6 @@
 #include <unistd.h>
 #include <signal.h>
 
-#include <boost/lexical_cast.hpp>
-
 #include <atomic>
 #include <functional>
 #include <map>
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 103ce4232b3..99fbcaf9daa 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -7,6 +7,8 @@
 #include <regex>
 
 #include <sodium.h>
+#include <boost/lexical_cast.hpp>
+#include <stdint.h>
 
 #ifdef NDEBUG
 #error "Nix may not be built with assertions disabled (i.e. with -DNDEBUG)."
@@ -111,6 +113,43 @@ std::string rewriteStrings(std::string s, const StringMap & rewrites)
     return s;
 }
 
+template<class N>
+std::optional<N> string2Int(const std::string_view s)
+{
+    if (s.substr(0, 1) == "-" && !std::numeric_limits<N>::is_signed)
+        return std::nullopt;
+    try {
+        return boost::lexical_cast<N>(s.data(), s.size());
+    } catch (const boost::bad_lexical_cast &) {
+        return std::nullopt;
+    }
+}
+
+// Explicitly instantiated in one place for faster compilation
+template std::optional<unsigned char>  string2Int<unsigned char>(const std::string_view s);
+template std::optional<unsigned short> string2Int<unsigned short>(const std::string_view s);
+template std::optional<unsigned int> string2Int<unsigned int>(const std::string_view s);
+template std::optional<unsigned long> string2Int<unsigned long>(const std::string_view s);
+template std::optional<unsigned long long> string2Int<unsigned long long>(const std::string_view s);
+template std::optional<signed char> string2Int<signed char>(const std::string_view s);
+template std::optional<signed short> string2Int<signed short>(const std::string_view s);
+template std::optional<signed int> string2Int<signed int>(const std::string_view s);
+template std::optional<signed long> string2Int<signed long>(const std::string_view s);
+template std::optional<signed long long> string2Int<signed long long>(const std::string_view s);
+
+template<class N>
+std::optional<N> string2Float(const std::string_view s)
+{
+    try {
+        return boost::lexical_cast<N>(s.data(), s.size());
+    } catch (const boost::bad_lexical_cast &) {
+        return std::nullopt;
+    }
+}
+
+template std::optional<double> string2Float<double>(const std::string_view s);
+template std::optional<float> string2Float<float>(const std::string_view s);
+
 
 bool hasPrefix(std::string_view s, std::string_view prefix)
 {
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 8b049875a89..0919f43c3a3 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -5,7 +5,6 @@
 #include "error.hh"
 #include "logging.hh"
 
-#include <boost/lexical_cast.hpp>
 
 #include <functional>
 #include <map>
@@ -102,16 +101,7 @@ std::string rewriteStrings(std::string s, const StringMap & rewrites);
  * Parse a string into an integer.
  */
 template<class N>
-std::optional<N> string2Int(const std::string_view s)
-{
-    if (s.substr(0, 1) == "-" && !std::numeric_limits<N>::is_signed)
-        return std::nullopt;
-    try {
-        return boost::lexical_cast<N>(s.data(), s.size());
-    } catch (const boost::bad_lexical_cast &) {
-        return std::nullopt;
-    }
-}
+std::optional<N> string2Int(const std::string_view s);
 
 /**
  * Like string2Int(), but support an optional suffix 'K', 'M', 'G' or
@@ -141,14 +131,7 @@ N string2IntWithUnitPrefix(std::string_view s)
  * Parse a string into a float.
  */
 template<class N>
-std::optional<N> string2Float(const std::string_view s)
-{
-    try {
-        return boost::lexical_cast<N>(s.data(), s.size());
-    } catch (const boost::bad_lexical_cast &) {
-        return std::nullopt;
-    }
-}
+std::optional<N> string2Float(const std::string_view s);
 
 
 /**
diff --git a/src/nix-env/user-env.cc b/src/nix-env/user-env.cc
index f7b091f8f56..5246b03e4cd 100644
--- a/src/nix-env/user-env.cc
+++ b/src/nix-env/user-env.cc
@@ -9,8 +9,9 @@
 #include "eval-inline.hh"
 #include "profiles.hh"
 #include "print-ambiguous.hh"
-#include <limits>
 
+#include <limits>
+#include <sstream>
 
 namespace nix {
 
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 0363ca8294a..27287a1a87a 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -14,6 +14,7 @@
 
 #include <iterator>
 #include <memory>
+#include <sstream>
 #include <nlohmann/json.hpp>
 #include <algorithm>