diff --git a/jscomp/others/belt_Float.ml b/jscomp/others/belt_Float.ml
index ed9c8fc7eb..c5da4af801 100644
--- a/jscomp/others/belt_Float.ml
+++ b/jscomp/others/belt_Float.ml
@@ -32,7 +32,7 @@ external toInt: float -> int = "%intoffloat"
 
 external fromInt: int -> float = "%identity"
 
-external fromString: string -> float = "parseFloat" [@@bs.val]
+external fromString: string -> float = "Number" [@@bs.val]
 
 let fromString i =
   match (fromString i) with
diff --git a/jscomp/others/belt_Int.ml b/jscomp/others/belt_Int.ml
index c03ce007c1..f6bb92685e 100644
--- a/jscomp/others/belt_Int.ml
+++ b/jscomp/others/belt_Int.ml
@@ -32,7 +32,7 @@ external toFloat: int -> float = "%identity"
 
 external fromFloat: float -> int = "%intoffloat"
 
-external fromString: string -> (_ [@bs.as 10]) -> int = "parseInt" [@@bs.val]
+external fromString: string -> (_ [@bs.as 10]) -> int = "Math.trunc" [@@bs.val]
 
 let fromString i =
   match fromString i with
diff --git a/jscomp/test/bs_float_test.ml b/jscomp/test/bs_float_test.ml
index f6e4efb244..aa780ded57 100644
--- a/jscomp/test/bs_float_test.ml
+++ b/jscomp/test/bs_float_test.ml
@@ -29,7 +29,16 @@ let () =
   eq __LOC__ (F.fromString "-1.0") (Some (-1.0));
   eq __LOC__ (F.fromString "-1.5") (Some (-1.5));
   eq __LOC__ (F.fromString "-1.7") (Some (-1.7));
-  eq __LOC__ (F.fromString "not a float") None
+  eq __LOC__ (F.fromString "17e-1") (Some (1.7));
+  eq __LOC__ (F.fromString "-17e-1") (Some (-1.7));
+  eq __LOC__ (F.fromString "  -17e-1  ") (Some (-1.7));
+  eq __LOC__ (F.fromString "0x11") (Some (17.));
+  eq __LOC__ (F.fromString "0b11") (Some (3.));
+  eq __LOC__ (F.fromString "0o11") (Some (9.));
+  eq __LOC__ (F.fromString "") (Some (0.));
+  eq __LOC__ (F.fromString "not a float") None;
+  eq __LOC__ (F.fromString "100.0abcdef") None;
+  eq __LOC__ (F.fromString "123_456.7") None
 
 let () =
   eq __LOC__ (F.toString 1.0) "1";
diff --git a/jscomp/test/bs_int_test.ml b/jscomp/test/bs_int_test.ml
index 0e90c5e0c1..b1cf58f5f0 100644
--- a/jscomp/test/bs_int_test.ml
+++ b/jscomp/test/bs_int_test.ml
@@ -29,7 +29,16 @@ let () =
   eq __LOC__ (I.fromString "-1.0") (Some (-1));
   eq __LOC__ (I.fromString "-1.5") (Some (-1));
   eq __LOC__ (I.fromString "-1.7") (Some (-1));
-  eq __LOC__ (I.fromString "not an int") None
+  eq __LOC__ (I.fromString "17e-1") (Some (1));
+  eq __LOC__ (I.fromString "-17e-1") (Some (-1));
+  eq __LOC__ (I.fromString "  -17e-1  ") (Some (-1));
+  eq __LOC__ (I.fromString "0x11") (Some (17));
+  eq __LOC__ (I.fromString "0b11") (Some (3));
+  eq __LOC__ (I.fromString "0o11") (Some (9));
+  eq __LOC__ (I.fromString "") (Some (0));
+  eq __LOC__ (I.fromString "not an int") None;
+  eq __LOC__ (I.fromString "100abcdef") None;
+  eq __LOC__ (I.fromString "123_456") None
 
 let () =
   eq __LOC__ (I.toString 1) "1";