diff --git a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
index 0e899e3e7051e..584eab6527a65 100644
--- a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
+++ b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
@@ -152,6 +152,7 @@ public class S3AFileSystem extends FileSystem {
    *   for this FileSystem
    * @param conf the configuration
    */
+  @SuppressWarnings("deprecation")
   public void initialize(URI name, Configuration conf) throws IOException {
     super.initialize(name, conf);
     setConf(conf);
@@ -181,7 +182,7 @@ public void initialize(URI name, Configuration conf) throws IOException {
       longOption(conf, FS_S3A_BLOCK_SIZE, DEFAULT_BLOCKSIZE, 1);
       enableMultiObjectsDelete = conf.getBoolean(ENABLE_MULTI_DELETE, true);
 
-      readAhead = longOption(conf, READAHEAD_RANGE, DEFAULT_READAHEAD_RANGE, 0);
+      readAhead = longByteOption(conf, READAHEAD_RANGE, DEFAULT_READAHEAD_RANGE, 0);
       storageStatistics = (S3AStorageStatistics)
           GlobalStorageStatistics.INSTANCE
               .put(S3AStorageStatistics.NAME,
@@ -1868,10 +1869,11 @@ private ObjectMetadata cloneObjectMetadata(ObjectMetadata source) {
    */
   @Deprecated
   public long getDefaultBlockSize() {
-    return getConf().getLong(FS_S3A_BLOCK_SIZE, DEFAULT_BLOCKSIZE);
+    return getConf().getLongBytes(FS_S3A_BLOCK_SIZE, DEFAULT_BLOCKSIZE);
   }
 
   @Override
+  @SuppressWarnings("deprecation")
   public String toString() {
     final StringBuilder sb = new StringBuilder(
         "S3AFileSystem{");
diff --git a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AUtils.java b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AUtils.java
index c89f6904cdaa6..22aa10ca74584 100644
--- a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AUtils.java
+++ b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AUtils.java
@@ -462,6 +462,27 @@ static long longOption(Configuration conf,
     return v;
   }
 
+  /**
+   * Get a long option >= the minimum allowed value, supporting memory
+   * prefixes K,M,G,T,P.
+   * @param conf configuration
+   * @param key key to look up
+   * @param defVal default value
+   * @param min minimum value
+   * @return the value
+   * @throws IllegalArgumentException if the value is below the minimum
+   */
+  static long longByteOption(Configuration conf,
+      String key,
+      long defVal,
+      long min) {
+    long v = conf.getLongBytes(key, defVal);
+    Preconditions.checkArgument(v >= min,
+        String.format("Value of %s: %d is below the minimum value %d",
+            key, v, min));
+    return v;
+  }
+
   /**
    * Get a size property from the configuration: this property must
    * be at least equal to {@link Constants#MULTIPART_MIN_SIZE}.
@@ -474,7 +495,7 @@ static long longOption(Configuration conf,
    */
   public static long getMultipartSizeProperty(Configuration conf,
       String property, long defVal) {
-    long partSize = conf.getLong(property, defVal);
+    long partSize = conf.getLongBytes(property, defVal);
     if (partSize < MULTIPART_MIN_SIZE) {
       LOG.warn("{} must be at least 5 MB; configured value is {}",
           property, partSize);