diff --git a/core/common/src/Sinks.kt b/core/common/src/Sinks.kt
index c2e87a66..4589daa4 100644
--- a/core/common/src/Sinks.kt
+++ b/core/common/src/Sinks.kt
@@ -87,35 +87,7 @@ public fun Sink.writeDecimalLong(long: Long) {
         negative = true
     }
 
-    // Binary search for character width which favors matching lower numbers.
-    var width =
-        if (v < 100000000L)
-            if (v < 10000L)
-                if (v < 100L)
-                    if (v < 10L) 1
-                    else 2
-                else if (v < 1000L) 3
-                else 4
-            else if (v < 1000000L)
-                if (v < 100000L) 5
-                else 6
-            else if (v < 10000000L) 7
-            else 8
-        else if (v < 1000000000000L)
-            if (v < 10000000000L)
-                if (v < 1000000000L) 9
-                else 10
-            else if (v < 100000000000L) 11
-            else 12
-        else if (v < 1000000000000000L)
-            if (v < 10000000000000L) 13
-            else if (v < 100000000000000L) 14
-            else 15
-        else if (v < 100000000000000000L)
-            if (v < 10000000000000000L) 16
-            else 17
-        else if (v < 1000000000000000000L) 18
-        else 19
+    var width = countDigitsIn(v)
     if (negative) {
         ++width
     }
@@ -135,6 +107,34 @@ public fun Sink.writeDecimalLong(long: Long) {
     }
 }
 
+private fun countDigitsIn(v: Long): Int {
+    val guess = ((64 - v.countLeadingZeroBits()) * 10) ushr 5
+    return guess + (if (v > DigitCountToLargestValue[guess]) 1 else 0)
+}
+
+private val DigitCountToLargestValue = longArrayOf(
+    -1, // Every value has more than 0 digits.
+    9L, // For 1 digit (index 1), the largest value is 9.
+    99L,
+    999L,
+    9999L,
+    99999L,
+    999999L,
+    9999999L,
+    99999999L,
+    999999999L,
+    9999999999L,
+    99999999999L,
+    999999999999L,
+    9999999999999L,
+    99999999999999L,
+    999999999999999L,
+    9999999999999999L,
+    99999999999999999L,
+    999999999999999999L, // For 18 digits (index 18), the largest value is 999999999999999999.
+    Long.MAX_VALUE, // For 19 digits (index 19), the largest value is MAX_VALUE.
+)
+
 /**
  * Writes [long] to this sink in hexadecimal form (i.e., as a string in base 16).
  *
diff --git a/core/common/test/AbstractSinkTest.kt b/core/common/test/AbstractSinkTest.kt
index f52f5eb7..2c1b57e0 100644
--- a/core/common/test/AbstractSinkTest.kt
+++ b/core/common/test/AbstractSinkTest.kt
@@ -343,6 +343,42 @@ abstract class AbstractSinkTest internal constructor(
         assertLongDecimalString("10000000000000000", 10000000000000000L)
         assertLongDecimalString("100000000000000000", 100000000000000000L)
         assertLongDecimalString("1000000000000000000", 1000000000000000000L)
+        assertLongDecimalString("-9", -9L)
+        assertLongDecimalString("-99", -99L)
+        assertLongDecimalString("-999", -999L)
+        assertLongDecimalString("-9999", -9999L)
+        assertLongDecimalString("-99999", -99999L)
+        assertLongDecimalString("-999999", -999999L)
+        assertLongDecimalString("-9999999", -9999999L)
+        assertLongDecimalString("-99999999", -99999999L)
+        assertLongDecimalString("-999999999", -999999999L)
+        assertLongDecimalString("-9999999999", -9999999999L)
+        assertLongDecimalString("-99999999999", -99999999999L)
+        assertLongDecimalString("-999999999999", -999999999999L)
+        assertLongDecimalString("-9999999999999", -9999999999999L)
+        assertLongDecimalString("-99999999999999", -99999999999999L)
+        assertLongDecimalString("-999999999999999", -999999999999999L)
+        assertLongDecimalString("-9999999999999999", -9999999999999999L)
+        assertLongDecimalString("-99999999999999999", -99999999999999999L)
+        assertLongDecimalString("-999999999999999999", -999999999999999999L)
+        assertLongDecimalString("-10", -10L)
+        assertLongDecimalString("-100", -100L)
+        assertLongDecimalString("-1000", -1000L)
+        assertLongDecimalString("-10000", -10000L)
+        assertLongDecimalString("-100000", -100000L)
+        assertLongDecimalString("-1000000", -1000000L)
+        assertLongDecimalString("-10000000", -10000000L)
+        assertLongDecimalString("-100000000", -100000000L)
+        assertLongDecimalString("-1000000000", -1000000000L)
+        assertLongDecimalString("-10000000000", -10000000000L)
+        assertLongDecimalString("-100000000000", -100000000000L)
+        assertLongDecimalString("-1000000000000", -1000000000000L)
+        assertLongDecimalString("-10000000000000", -10000000000000L)
+        assertLongDecimalString("-100000000000000", -100000000000000L)
+        assertLongDecimalString("-1000000000000000", -1000000000000000L)
+        assertLongDecimalString("-10000000000000000", -10000000000000000L)
+        assertLongDecimalString("-100000000000000000", -100000000000000000L)
+        assertLongDecimalString("-1000000000000000000", -1000000000000000000L)
     }
 
     private fun assertLongDecimalString(string: String, value: Long) {