diff --git a/README.md b/README.md
index 2f3242bd..ff0dff66 100644
--- a/README.md
+++ b/README.md
@@ -167,7 +167,7 @@ int length = sprintf(NULL, "Hello, world"); // length is set to 12
 | PRINTF_NTOA_BUFFER_SIZE            | 32        | ntoa (integer) conversion buffer size. This must be big enough to hold one converted numeric number _including_ leading zeros, normally 32 is a sufficient value. Created on the stack |
 | PRINTF_FTOA_BUFFER_SIZE            | 32        | ftoa (float) conversion buffer size. This must be big enough to hold one converted float number _including_ leading zeros, normally 32 is a sufficient value. Created on the stack |
 | PRINTF_DEFAULT_FLOAT_PRECISION     | 6         | Define the default floating point precision |
-| PRINTF_MAX_FLOAT                   | 1e9       | Define the largest suitable value to be printed with %f, before using exponential representation |
+| PRINTF_MAX_FLOAT                   | 1e9       | Define the largest suitable value to be printed with %f, before using exponential representation. Note that this must be set to a value which fits in a 64-bit signed integer (i.e. less than 2^63) |
 | PRINTF_DISABLE_SUPPORT_FLOAT       | undefined | Define this to disable floating point (%f) support |
 | PRINTF_DISABLE_SUPPORT_EXPONENTIAL | undefined | Define this to disable exponential floating point (%e) support |
 | PRINTF_DISABLE_SUPPORT_LONG_LONG   | undefined | Define this to disable long long (%ll) support |
diff --git a/printf.c b/printf.c
index 0e9494e8..b77a1df5 100644
--- a/printf.c
+++ b/printf.c
@@ -382,7 +382,7 @@ static size_t _ftoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, d
     prec--;
   }
 
-  int whole = (int)value;
+  int_fast64_t whole = (int_fast64_t)value;
   double tmp = (value - whole) * pow10[prec];
   unsigned long frac = (unsigned long)tmp;
   diff = tmp - (double)frac;
diff --git a/test/test_suite.cpp b/test/test_suite.cpp
index bffc3891..ca4d02bc 100644
--- a/test/test_suite.cpp
+++ b/test/test_suite.cpp
@@ -1225,6 +1225,48 @@ TEST_CASE("float", "[]" ) {
   test::sprintf(buffer, "%.3f", 30343.1415354);
   REQUIRE(!strcmp(buffer, "30343.142"));
 
+  // switch from decimal to exponential representation
+  //
+  test::sprintf(buffer, "%.0f", (double) ((int64_t)1 * 1000 ) );
+  if (PRINTF_MAX_FLOAT < 10e+2) {
+    REQUIRE(!strcmp(buffer, "10e+2"));
+  }
+  else {
+    REQUIRE(!strcmp(buffer, "1000"));
+  }
+
+  test::sprintf(buffer, "%.0f", (double) ((int64_t)1 * 1000 * 1000 ) );
+  if (PRINTF_MAX_FLOAT < 10e+5) {
+    REQUIRE(!strcmp(buffer, "10e+5"));
+  }
+  else {
+    REQUIRE(!strcmp(buffer, "1000000"));
+  }
+
+  test::sprintf(buffer, "%.0f", (double) ((int64_t)1 * 1000 * 1000 * 1000 ) );
+  if (PRINTF_MAX_FLOAT < 10e+8) {
+    REQUIRE(!strcmp(buffer, "10e+8"));
+  }
+  else {
+    REQUIRE(!strcmp(buffer, "1000000000"));
+  }
+
+  test::sprintf(buffer, "%.0f", (double) ((int64_t)1 * 1000 * 1000 * 1000 * 1000) );
+  if (PRINTF_MAX_FLOAT < 10e+11) {
+    REQUIRE(!strcmp(buffer, "10e+11"));
+  }
+  else {
+    REQUIRE(!strcmp(buffer, "1000000000000"));
+  }
+
+  test::sprintf(buffer, "%.0f", (double) ((int64_t)1 * 1000 * 1000 * 1000 * 1000 * 1000) );
+  if (PRINTF_MAX_FLOAT < 10e+14) {
+    REQUIRE(!strcmp(buffer, "10e+14"));
+  }
+  else {
+    REQUIRE(!strcmp(buffer, "1000000000000000"));
+  }
+
   test::sprintf(buffer, "%.0f", 34.1415354);
   REQUIRE(!strcmp(buffer, "34"));