diff --git a/src/ncurses_ui.cc b/src/ncurses_ui.cc
index e275bbf0..a4ec7586 100644
--- a/src/ncurses_ui.cc
+++ b/src/ncurses_ui.cc
@@ -904,16 +904,14 @@ void NCursesUI::set_ui_options(const Options& options)
         auto wheel_down_it = options.find("ncurses_wheel_down_button");
         if (wheel_down_it == options.end())
             m_wheel_down_button = 2;
-        else try {
-            m_wheel_down_button = str_to_int(wheel_down_it->second);;
-        } catch(...) {}
+        else if (auto down = str_to_int_ifp(wheel_down_it->second))
+            m_wheel_down_button = *down;
 
         auto wheel_up_it = options.find("ncurses_wheel_up_button");
         if (wheel_up_it == options.end())
             m_wheel_up_button = 4;
-        else try {
-            m_wheel_up_button = str_to_int(wheel_up_it->second);;
-        } catch(...) {}
+        else if (auto up = str_to_int_ifp(wheel_up_it->second))
+            m_wheel_up_button = *up;
     }
 }
 
diff --git a/src/optional.hh b/src/optional.hh
index 57147b43..67b2352a 100644
--- a/src/optional.hh
+++ b/src/optional.hh
@@ -1,6 +1,8 @@
 #ifndef optional_hh_INCLUDED
 #define optional_hh_INCLUDED
 
+#include "assert.hh"
+
 namespace Kakoune
 {
 
diff --git a/src/string.cc b/src/string.cc
index bc02b4a3..2735f087 100644
--- a/src/string.cc
+++ b/src/string.cc
@@ -98,7 +98,7 @@ String indent(StringView str, StringView indent)
     return res;
 }
 
-int str_to_int(StringView str)
+Optional<int> str_to_int_ifp(StringView str)
 {
     unsigned int res = 0;
     bool negative = false;
@@ -110,11 +110,18 @@ int str_to_int(StringView str)
         else if (c >= '0' and c <= '9')
             res = res * 10 + c - '0';
         else
-            throw runtime_error(str + "is not a number");
+            return {};
     }
     return negative ? -(int)res : (int)res;
 }
 
+int str_to_int(StringView str)
+{
+    if (auto val = str_to_int_ifp(str))
+        return *val;
+    throw str + " is not a number";
+}
+
 InplaceString<16> to_string(int val)
 {
     InplaceString<16> res;
diff --git a/src/string.hh b/src/string.hh
index da235744..b5ad8e5a 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -1,11 +1,12 @@
 #ifndef string_hh_INCLUDED
 #define string_hh_INCLUDED
 
+#include "array_view.hh"
+#include "hash.hh"
+#include "optional.hh"
 #include "units.hh"
 #include "utf8.hh"
-#include "hash.hh"
 #include "vector.hh"
-#include "array_view.hh"
 
 #include <string>
 #include <climits>
@@ -256,7 +257,8 @@ inline String codepoint_to_str(Codepoint cp)
     return str;
 }
 
-int str_to_int(StringView str);
+int str_to_int(StringView str); // throws on error
+Optional<int> str_to_int_ifp(StringView str);
 
 template<size_t N>
 struct InplaceString