diff --git a/four2.f b/four2.f
index 0a2e78c25..b3f4aeaa9 100755
--- a/four2.f
+++ b/four2.f
@@ -36,7 +36,8 @@ C     the naive NTOT**2.  Furthermore, less error is built up.
 C     Written by Norman Brenner of MIT Lincoln Laboratory, January 1969.
 C     See IEEE Audio Transactions (June 1967), Special issue on FFT.
 
-      DIMENSION DATA(1048576), N(1)
+      parameter(NMAX=2048*1024)
+      DIMENSION DATA(NMAX), N(1)
       NTOT=1
       DO 10 IDIM=1,NDIM
  10   NTOT=NTOT*N(IDIM)
@@ -78,7 +79,8 @@ C     EXCHANGE DATA(J1,J4REV,J5) WITH DATA(J1,J4,J5) FOR ALL J1 FROM 1
 C     TO NPREV, ALL J4 FROM 1 TO N (WHICH MUST BE A POWER OF TWO), AND
 C     ALL J5 FROM 1 TO NREM.  J4REV-1 IS THE BIT REVERSAL OF J4-1.  E.G.
 C     SUPPOSE N = 32.  THEN FOR J4-1 = 10011, J4REV-1 = 11001, ETC.
-      DIMENSION DATA(1048576)
+      parameter(NMAX=2048*1024)
+      DIMENSION DATA(NMAX)
       IP0=2
       IP1=IP0*NPREV
       IP4=IP1*N
@@ -135,7 +137,8 @@ C     IT IS NOT NECESSARY TO REWRITE THIS SUBROUTINE INTO COMPLEX
 C     NOTATION SO LONG AS THE FORTRAN COMPILER USED STORES REAL AND
 C     IMAGINARY PARTS IN ADJACENT STORAGE LOCATIONS.  IT MUST ALSO
 C     STORE ARRAYS WITH THE FIRST SUBSCRIPT INCREASING FASTEST.
-      DIMENSION DATA(1048576)
+      parameter(NMAX=2048*1024)
+      DIMENSION DATA(NMAX)
 
       real*8 twopi,wstpr,wstpi,wr,wi,w2r,w2i,w3r,w3i,wtempr
 
@@ -255,7 +258,8 @@ C     DATA(I1,I2) = (DATA(I1,I2)-TEMP)*(1-IFORM)
 C 10  DATA(I1CNJ,I2) = (DATA(I1CNJ,I2)+CONJ(TEMP))*(1-IFORM)
 C     IF I1=I1CNJ, THE CALCULATION FOR THAT VALUE COLLAPSES INTO
 C     A SIMPLE CONJUGATION OF DATA(I1,I2).
-      DIMENSION DATA(2)
+      parameter(NMAX=2048*1024)
+      DIMENSION DATA(NMAX)
       TWOPI=6.283185307*FLOAT(ISIGN)
       IP0=2
       IP1=IP0*(N/2)