Index: Python/pystrtod.c
===================================================================
--- Python/pystrtod.c	(revision 59545)
+++ Python/pystrtod.c	(working copy)
@@ -238,6 +238,30 @@
 		}
 	}
 
+	/* Ensure that the exponent is at least 3 digits,
+	   providing the buffer is large enough for the extra zeros. */
+	p = buffer;
+	while (*p && *p != 'e' && *p != 'E')
+		++p;
+	if (*p && (*(p + 1) == '-' || *(p + 1) == '+')) {
+		char *start = p + 2;
+		int exponent_digit_count = 0;
+		int zeros = 0;
+		p += 2;
+		while (*p && isdigit((unsigned char)*p)) {
+			++p;
+			++exponent_digit_count;
+		}
+		zeros = 3 - exponent_digit_count;
+		if (exponent_digit_count && zeros > 0 &&
+		    start + zeros + exponent_digit_count + 1
+		    < buffer + buf_len) {
+			p = start;
+			memmove(p + zeros, p, exponent_digit_count + 1);
+			memset(p, '0', zeros);
+		}
+	}
+
 	return buffer;
 }