diff --git a/spec/std/json/lexer_spec.cr b/spec/std/json/lexer_spec.cr
index 55437b44c0ec..7a2fe61de23c 100644
--- a/spec/std/json/lexer_spec.cr
+++ b/spec/std/json/lexer_spec.cr
@@ -114,4 +114,5 @@ describe JSON::Lexer do
   it_lexes_float "9000000000000000000.0", 9000000000000000000.0
   it_lexes_float "9876543212345678987654321.0", 9876543212345678987654321.0
   it_lexes_float "9876543212345678987654321e20", 9876543212345678987654321e20
+  it_lexes_float "10.100000000000000000000", 10.1
 end
diff --git a/src/json/lexer.cr b/src/json/lexer.cr
index 4057b81d1661..ab4d25baf5ff 100644
--- a/src/json/lexer.cr
+++ b/src/json/lexer.cr
@@ -283,6 +283,7 @@ abstract class JSON::Lexer
       integer *= 10
       integer += char - '0'
       divisor *= 10
+      digits += 1
       char = next_char
     end
     float = integer.to_f64 / divisor